t)i    3 

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1  ir"  s 


A  condensed  and  reliable  treatise,  giving 

full  directions  for  the  construction 

and  operation  of  any  kind  of 

electrical  apparatus 


COPYRIGHT  1902  BY  GEORGE  L.  Fowuot 


CONTENTS 


CHAP.  PAGE 

I      ELECTRICITY  AND  MAGNETISM  ...         5 

II      STATICAL  ELECTRICITY,  THE  PLATE  MACHINE 

AND  THE  LEYDEN  JAR         .  .  .  .14 

III  CONDUCTORS,  CONNECTIONS,  INSULATION    AND 

BATTERIES 26 

IV  ELECTRIC  BELLS 47 

V      THE  ELECTRIC  TELEGRAPH       .  .69 

VI      THE  TELEPHONE     0 87 

VII      DYNAMOS  AND  MOTORS 106 

VIII      ELECTRIC  LIGHTING 123 

IX  ELECTRO-PLATING  ,.,.-.-,           .           ,            .144 

X      STORAGE  BATTERIES 160 

XI  TRANSFORMERS       ...      .           .           ,,        ....        .    172 

XII  BURGLAR  ALARMS  AND  GAS  LIGHTING      .           .179 

XIII  ELECTRICAL  EXPERIMENTS       .            .            .            .194 

GLOSSARY 200 

431656 


Electricity 


CHAPTER  I 

ELECTRICITY   AND   MAGNETISM 

THE  manifestations  of  electrical  phenomena 
have  been  known  to  man  ever  since  he  first 
came  to  consciousness,  in  the  misty  ages  of  the 
past.  It  is  quite  true  that  he  did  not  recognize 
them  as  such  but  attributed  them  to  the  anger 
or  pleasure  of  his  gods  according  as  they  were 
terrifying  or  attractive.  It  is  far  easier  to  con- 
ceive a  superstitious  cause  for  natural  phenomena 
than  it  is  to  search  out  the  hidden  secrets  of 
nature  and  learn  the  true  reason  for  the  other- 
wise inexplicable  things  that  occur  before  our 
eyes. 

So,  while  man  must  have  observed  the  forces 
that  we  now  know  to  be  merely  manifestations 

5 


6  Electricity 

of  that  subtle  influence,  which  we  call  electricity, 
from  the  earliest  age^  01  his  existence,  the  first 
recorded  observance  of  it  cemes  to  us  from  the 
Greeks. 

They  had  found  that  the  beautiful  amber  pos- 
sessed, when  rubbed  with  a  cloth  or  fur,  the 
power  of  attracting  to  itself  light  particles  of 
dust  or  parchment.  Like  all  other  supersti- 
tious people  they  attributed  this  action  to  the 
spirit  that  dwelt  within  the  amber  and  which 
was  aroused  to  action  by  the  warmth  generated 
by  the  friction  of  the  rubbing.  It  was  a  slight 
matter  but,  nevertheless,  it  was  so  invariable  in 
its  action  and  was  so  peculiar  to  this  one  sub- 
stance that  the  Greek  name  for  amber  or  "  elec- 
tron," has  been  handed  down  through  the  cen- 
turies as  that  of  the  wonderfully  subtle  force 
that  is  revolutionizing  the  world  and  which  bids 
fair  to  have  an  era  of  its  own  just  as  we  have 
had  the  eras  of  bronze  and  iron  and  silver  and 
gold. 

The  manifestations  of  attraction  and  repulsion 
of  the  amber  or  electron  were  noted  first  as  a 
superstition ;  then  as  an  indifferent  matter  of 
e very-day  occurrence  and  finally  as  a  subject 
worthy  of  scientific  investigation  and  in- 
quiry. 


jeiectdcftE  anD  /toagnettem  7 

Meanwhile  in  the  heavens  above  and  the  earth 
beneath  there  were  greater  and  more  imposing 
manifestations  of  this  same  force,  but  on  a  scale 
so  grand  that  the  untrained  minds  of  the  men 
before  whom  they  appeared  could  not  conceive 
of  the  possibility  of  connecting  the  one  with  the 
other.  What  possible  relationship  could  exist 
between  the  blinding  flash  of  lightning  and  the 
deafening  roar  of  the  thunder,  or  the  soft  scintil- 
lating light  of  the  aurora  borealis  and  that  yellow 
bit  of  amber  in  a  woman's  hand  that  silently 
draws  the  dust  or  threads  of  cotton  to  itself  ?  It 
was  far  easier  to  attribute  one  to  the  bolts  of  an 
angry  god  or  the  warfare  of  the  demons  of  the 
air,  the  other  to  the  reflected  light  from  the  ban- 
queting halls  of  the  rulers  of  earth  and  sky,  and 
the  last  to  the  spirit  sleeping  within  the  bit  of 
gum,  than  connect  the  three  into  different  mani- 
festations of  one  and  the  same  power,  differing 
only  in  intensity  and  not  in  kind.  Surely  noth- 
ing could  appear  more  widely  different  than  the 
flash  of  the  lightning,  the  scintillation  of  the 
northern  light  and  the  fluttering  of  a  bit  of 
paper  about  a  piece  of  amber.  Yet  we  have 
learned  that  they  are  the  same  in  kind  and  differ 
only  in  degree. 

For  many  centuries  the  world  was  quite  con- 


8  BlectrtcttB 

tent  to  stand  in  wonder  and  awe  at  what  it  saw 
with  never  a  thought  of  search  or  investigation. 
It  was  not  until  the  sixteenth  century  that  any- 
thing approaching  a  scientific  inquiry  was  made 
into  the  peculiarities  of  the  manifestations  of  the 
rubbed  amber.  At  first  progress  dragged  and 
nearly  three  centuries  were  to  elapse  before  the 
electric  manifestations  were  to  be  harnessed  so 
as  to  do  duty  in  the  service  of  mankind.  In  fact 
it  was  not  until  the  second  quarter  of  the  eight- 
eenth century  that  there  was  any  clear  concep- 
tion of  the  electrical  properties  of  different  sub- 
stances. The  first  step  was  the  discovery  of  the 
difference  existing  when  friction  was  applied  to 
different  materials.  It  led  to  the  division  of 
electricity  into  two  kinds ;  the  vitreous  and  res- 
inous. The  former  was  supposed  to  be  produced 
when  friction  was  applied  to  amber,  sealing  wax 
or  any  other  resinous  substance.  Yitreous  elec- 
tricity was  excited  when  friction  was  applied  to 
glass,  rock,  crystal  or  the  precious  stones.  It 
was  also  seen  that  the  objects  charged  with  a 
similar  electricity  repelled  each  other  and  that 
those  charged  with  dissimilar  attracted.  The 
more  modern  investigations  have  shown  that  it 
is  a  case  of  polarity  rather  than  a  true  difference 
and  that  the  vitreous  electricity  corresponds  to  a 


Electricity  anD  /flbaanetfsm  9 

positive  and  the  resinous  to  what  is  known  as  a 
negative  charge. 

The  power  of  communicating  a  charge  from 
one  substance  to  another  and  the  conductivity  of 
certain  materials  by  which  the  electric  charge 
was  carried  from  one  point  to  another  followed 
and  it  was  found  that  the  metals  were  good  con- 
ductors while  glass,  porcelain,  silk,  cotton,  hair, 
etc.,  were  non-conductors  or  insulators.  The  fact 
is,  all  substances  are  conductors  and  it  would  be 
impossible  to  draw  a  hard  and  fast  line  on  either 
side  of  which  could  be  grouped  the  conductors 
and  non-conductors.  It  is  a  case  of  more  or  less 
resistance  to  the  passage  of  the  electric  current. 
In  the  case  of  silver  and  copper  the  resistance  is 
so  slight  that  these  metals  are  considered  to  be 
the  best  of  conductors.  In  iron  the  resistance  is 
greater,  but  still  not  so  great  as  to  debar  it  from 
being  considered  as  a  conductor  and  being  almost 
universally  used  for  telegraph  purposes.  When, 
however,  we  come  to  glass,  porcelain,  silk  and 
parafine  the  resistance  is  so  great  that  they  are 
said  to  be  non-conductors  or  insulators,  and  are 
used,  therefore,  as  a  means  of  support  for  those 
metals  that  are  employed  for  the  conduction  of 
an  electric  current  from  one  point  to  another. 

This  property  of  the  variation   in  electrical 


10  electricity 

charges  and  conductivity  of  metals  led  to  the 
discovery  of  the  Leyden  jar.  It  had  been  "  ob- 
served that  electrified  bodies  exposed  to  the  at- 
mosphere, speedily  lost  their  electric  charge,  the 
idea  was  conceived  of  surrounding  them  with  an 
insulating  substance,  by  which  it  was  thought 
that  their  electric  power  might  be  preserved  for 
a  longer  time."  Water  contained  in  a  glass  bot- 
tle was  accordingly  electrified,  but  no  remark- 
able results  were  obtained,  till  one  of  the  party 
who  was  holding  the  bottle,  attempted  to  dis- 
engage the  wire  communicating  with  the  prime 
conductor  of  a  powerful  machine ;  the  conse- 
quence was  that  he  received  a  shock,  which, 
though  slight  compared  with  such  as  are  fre- 
quently taken  for  amusement  from  a  Leyden  jar, 
his  fright  magnified  and  exaggerated  in  an 
amusing  manner.  In  describing  the  effect  pro- 
duced on  himself  he  says  "  that  he  felt  himself 
struck  in  his  arms,  shoulders  and  breast,  so  that 
he  lost  his  breath  and  it  was  two  days  before  he 
recovered  from  the  effects  of  the  blow  and 
terror,  and  that  he  would  not  take  a  second 
shock  for  the  kingdom  of  France." 

The  sparks  emitted  upon  the  discharge  of  a 
Leyden  jar,  owing  to  their  peculiar  character- 
istics led  Franklin  to  his  famous  experiments 


Blectrfcftg  and  /iRagnetism  n 

with  a  kite  by  which  he  succeeded  in  drawing 
electricity  from  the  clouds  and  charging  a  Ley- 
den  jar  and  thus  establishing  the  identity  of  the 
lightning  with  the  gentle  manifestation  of  the 
attraction  of  a  slip  of  paper  to  a  piece  of  rubbed 
ceiling-wax  or  amber. 

Another  natural  phenomena  which  is  closely 
associated  with  electricity  is  that  of  magnetism, 
though  for  centuries  it  was  regarded  as  en- 
tirely separate  and  distinct.  The  first  manifesta- 
tion of  magnetic  phenomena  to  be  observed  was 
that  of  the  loadstone  or  magnetic  iron  ore.  It 
was  found  that  a  piece  of  this  material  freely 
suspended  in  the  air  would  turn  in  a  certain 
definite  position  in  which  one  side  was  turned 
towards  the  north.  It  was  also  found  that  a 
piece  of  iron  rubbed  against  this  magnetic  iron 
ore  acquired  the  same  property  and  that  if  it 
were  done  with  steel  the  property  became  a  per- 
manent one.  This  led  to  the  discovery  of  the 
mariner's  compass. 

It  was  not,  however,  until  the  nineteenth 
century  that  the  connection  between  electricity 
and  magnetism  was  so  thoroughly  established 
that  it  became  possible  to  convert  the  manifesta- 
tions of  either  one  to  the  other. 

It  has  been  found  that  if  a  wire  is  bent  into  a 


12 


Blectricitg 


coil  as  shown  in  Fig.  1,  and  a  current  of  elec- 
tricity  be  made  to  pass  through  it  it  will  possess 
all  of  the  properties  of  a  magnet.  The  coil  here 
shown  is  that  known  as  a  left  hand  coil,  and  if  a 

current  be  pass- 
ed through  in 
the  direction  of 
the  arrows  from 
what  is  marked 
the  positive  (-f ) 
end  of  the  wire 

FIG.  I.-THE  SOLENOID  to  the  negati^ 

( — )  end,  and  it 

be  left  free  to  swing,  it  will  stand  with  its  X  end  to 
the  north  and  the  S  end  to  the  south  exactly  as 
the  compass  needle  will  do.  If  a  similar  current 
be  passed  through  such  a  coil  in  the  opposite  di- 
rection the  poles  will  be  reversed  and  the  posi- 
tion assumed  by  the  coil  when  allowed  to  swing 
freely  will  also  be  reversed. 

If  now  a  bar  of  soft  metal  be  placed  within 
such  a  coil  it  at  once  becomes  magnetized  with  a 
strength  that  depends  upon  the  number  of  coils 
and  the  intensity  of  the  current.  In  case  such  a 
piece  of  iron  is  free  to  move  it  will  travel 
through  the  coil  under  the  magnetic  influence  of 
the  electric  current  that  flows  through  the  wire. 


jeiectrfcftg  anD  flBasnettem  is 

As  the  electric  current  passing  through  the 
wire  possesses  the  power  to  magnetize  a  piece  of 
metal  that  is  within  it,  so  a  permanent  magnet 
moved  through  or  made  to  approach  or  recede 
from  the  coil  has  the  power  of  inducing  an  elec- 
tric current  through  the  wire. 

It  is  upon  this  mutual  interaction  of  the  cur- 
rent and  the  magnet  upon  each  other  that  the 
whole  field  of  modern  electric  operation  depends. 
The  dynamo  and  telegraph  instrument  are  the 
most  familiar  examples  of  this  action  as  will  be 
shown  later  on. 


CHAPTEE  II 

STATICAL    ELECTRICITY,   THE    PLATE   MACHINE 
AND  THE  LEYDEN  JAR 

WHEN  a  piece  of  ambef,  resin,  ceiling  wax  or 
glass  is  rubbed  and  an  electrical  condition  in- 
duced, it  is  said  to  be  charged  with  static  elec- 
tricity in  distinction  from  dynamic  electricity, 
which  will  be  explained  later.  This  static  elec- 
tricity is  of  such  a  character  that  if  the  charged 
body  be  brought  into  contact  with  another  body 
charged  with  the  opposite  kind,  the  two  will  flow 
together,  neutralize  each  other  and  cause  the 
instant  disappearance  of  every  trace  of  the  elec- 
trical charge. 

While  the  rubbing  of  a  piece  of  wax  or  amber 
may  be  quite  sufficient  to  charge  the  same  to  an 
extent  that  will  cause  it  to  attract  particles  of 
dust,  slips  of  paper  or  balls  of  pith,  it  will  be 
quite  insufficient  to  give  manifestations  requiring 
greater  power  such  as  the  production  of  a  spark. 

Then,  too,  it  has  been  found  that  the  electric 
charge  is  evenly  distributed  over  the  whole  sur- 
14 


Statical  Electricity 


15 


face  of  the  charged  body.  As  these  substances 
are  usually  bad  conductors  the  relief  of  the 
charge  is  slow  and  fails  to  meet  the  requirements 
of  experimental  or  practical  work. 

The  usual  method  of  generating  a  charge  of 
statical  electricity  is  by  the  use  of  what  is  known 
as  the  plate  machine  that  is  shown  in  Fig.  2. 

This  machine 
consists  of  a  cir- 
cular plate  of 
glass  that  is 
mounted  upon  a 
shaft  made  to  ^^ 
turn  in  a  wooden 
frame  by  means 
of  a  crank  and 
handle.  Press- 
ed to  either  side 
of  the  glass  at 
the  top  and  bot- 
tom is  a  rubber 
made  of  cloth, 
felt  or  soft  leather.  About  the  best  material 
to  use  for  this  purpose  is  a  soft  chamois  leather 
backed  by  a  cushion  so  that  it  exerts  an  even 
pressure  upon  the  glass.  By  placing  them  at  the 
top  and  bottom  and  on  both  sides  of  the  glass 


FIG.  2.— THE  PLATE  MACHINE 


16  BlectrtcftB 

the  pressure  is  equalized  and  distortion  of  the 
glass  plate  is  prevented. 

At  right  angles  to  the  rubbers  on  the  circle  of 
the  plate  there  is  a  frame  from  which  a  number 
of  sharp  points  project  which  are  brought  up  so 
that  they  are  almost  in  contact  with  the  plate. 
These  points  and  the  frame  to  which  they  are 
attached  are  connected  by  a  good  conductor  to 
what  is  known  as  the  prime  conductor.  The 
latter  is  usually  made  of  hollow  brass,  and  it  is 
supported  with  the  frame  and  its  pointers  upon 
glass  columns  so  as  to  insulate  it  from  the  main 
frame  of  the  machine. 

The  operation  of  such  a  machine  is  exceedingly 
simple.  The  plate  is  caused  to  revolve  and  the 
frictional  action  of  the  rubbers  upon  it  charges 
it  with  electricity.  As  the  successive  portions  of 
the  plate  pass  beneath  the  insulated  points  the 
charge  is  drawn  off  and  carried  by  them  to  the 
prime  conductor,  from  which  it  can  be  drawn  in 
turn  to  the  Leyden  jar  wherein  it  is  to  be  stored. 

In  making  such  an  electrical  machine  a  few 
necessary  precautions  must  be  taken  in  order  to 
secure  the  best  results.  The  glass  should  be  of 
a  good  quality  of  plate  glass  about  ^  inch  thick, 
and  should  be  so  mounted  upon  its  shaft  that 
when  the  latter  is  turned  in  its  bearings  the  plate 


Statical  Electricity  17 

will  run  true  and  without  wabbling.  The  rub- 
bers should  be  cushioned  by  packing  them  with 
some  soft,  yielding  and  yet  elastic  material  so 
that  they  may  exert  a  constant  and  even  pres- 
sure against  the  sides  of  the  plate.  The  frame 
upon  which  this  plate  with  its  shaft  is  mounted 
should  be  preferably  of  wood.  This  is  because 
wood  is  a  comparatively  bad  conductor  and  will 
tend  to  prevent  an  escape  of  the  charge  into 
the  earth  rather  than  into  the  prime  conductor 
whither  it  is  desired  that  it  should  go. 

It  is  a  peculiarity  of  this  method  of  generating 
electricity  that  if  a  piece  of  glass  is  rubbed  and 
thereby  excited  with  a  charge  of  positive  elec- 
tricity, the  material  used  as  a  rubber  is,  at  the 
same  time,  charged  with  negative  electricity. 
Now  if  the  two  are  kept  in  contact  these  oppo- 
site charges  will  flow  towards  each  other  and 
become  neutralized.  In  order  to  prevent  this  it 
is  necessary  that  the  negative  electricity  should 
be  removed  from  the  rubbers  of  the  plate  machine 
as  rapidly  as  it  is  generated.  In  order  to  do  this 
it  is  customary  to  place  a  chain  in  metallic  con- 
tact with  the  rubbers  and  allow  one  end  to  lie 
upon  the  table  or  floor  upon  which  the  machine 
rests,  This  enables  the  positive  electricity  exist- 
ing in  the  earth  to  approach  and  flow  up  to  the 


18  ^electricity 

rubber  and  render  it  inert  by  neutralizing  the 
charge  contained  therein.  Meanwhile  the  posi- 
tive charge  is  increasing  in  the  prime  conductor. 

The  form  of  the  prime  conductor  must  also 
receive  consideration.  It  should  be  made  hollow 
for  the  sake  of  lightness,  and  because  it  has  been 
found  that  an  electric  charge  distributes  itself 
over  the  outside  of  a  body  and  does  not  pene- 
trate the  interior. 

It  has  also  been  found  that  the  discharge  takes 
place  much  more  freely  from  sharp  points  and 
angles  than  it  does  from  rounded  surfaces.  For 
this  reason,  where  there  is  to  be  a  collection, 
special  discharge  points  are  used,  while  equal 
care  should  be  exercised  in  the  making  of  the 
prime  conductor  that  it  should  have  no  exterior 
angles  or  sharp  projections. 

As  for  dimensions — any  diameter  of  glass  can 
be  used,  but  it  will  be  found  that  a  convenient 
diameter  will  lie  between  18  inches  and  3  feet. 

When  operating  the  machine,  the  leathers 
should  be  occasionally  rubbed  over  with  an 
amalgam  of  zinc,  tin  and  mercury,  or  better  still 
with  the  bi-sulphuret  of  tin  which  is  one  of  the 
most  efficient  materials  for  exciting  on  glass. 

In  case  of  large  and  powerful  machines  it  is 
possible  to  mount  two  plates  upon  one  shaft. 


Statical  Blectrfcfts  19 

"When  such  a  machine  is  well  adjusted  and  is 
put  into  motion,  the  first  thing  to  be  noticed  is 
that  it  produces  a  crackling  noise  which  can  be 
located  at  the  collecting  points.  Then  if  the 
knuckles  of  the  hand  are  brought  near  the  prime 
conductor  a  spark  will  leap  across  the  interval 
between  them  with  a  sharp  snap,  causing  a  prick- 
ing sensation. 

If  now  the  room  be  darkened  various  mani- 
festations of  light  will  be  observed.  Brushes  of 
pale  blue  light  will  be  seen  to  emanate  from 
some  of  the  most  angular  portions  of  the  prime 
conductor  and  circles  of  light  will  snap  along 
over  the  face  of  the  glass  between  the  rubbers 
and  the  collectors.  Then  if  the  working  be  con- 
tinued for  any  length  of  time,  a  peculiar  odor 
can  be  detected  due  to  the  presence  of  ozone — 
that  seems  to  be  invariably  present  at  the  devel- 
opment of  electricity. 

The  peculiar  attractive  and  repellent  character- 
istics of  an  electric  charge  can  also  be  made  very 
manifest  in  connection  with  the  plate  machine. 
By  bringing  a  charged  body  near  another  which 
is  not  charged  there  will  be  an  attraction  of  the 
opposite  electricity  to  that  of  the  charged  body 
in  that  end  of  the  uncharged  one  that  is  nearest 
to  the  charged.  If  two  pith-balls  are  suspended 


20 


Blectricits 


from  the  end  of  either  body  they  will  be  charged 
with  electricity  corresponding  to  that  one.  Under 
the  influence  of  this  charge  they  will  be  repelled 
from  each  other.  Thus  a  physical  demonstration 
will  be  afforded  of  the  attraction  of  opposite  and 
the  repulsion  of  like  charges  of  electricity. 
The  Leyden  jar,  which  is  used  for  storing  or 
condensing  electricity  is  one  of  the 
simplest  if  not  the  very  simplest  of 
any  electrical  instrument  to  make. 
The  common  form  is  shown  in 
Fig.  3.  It  consists  of  a  glass  jar 
with  a  large  mouth  that  is  coated 
inside  and  out  for  about  two-thirds 
of  its  height  with  tinfoil.  Through 
the  stopper  a  brass  rod  having  a 
knob  at  the  upper  end  is  passed, 
and  the  lower  end  of  the  same  is 
connected  by  a  chain,  or  other 
metallic  conductor  to  the  inner  coat- 
ing. In  case  it  is  desired  to  make 
the  jar  without  going  to  the  trouble  of  coating 
the  interior  surface,  equally  good  results  can  be 
obtained  by  filling  the  jar  about  two-thirds  full 
of  foil  or  other  metallic  clippings. 

The  charging  of  a  Leyden  jar  is  exceedingly 
simple.     The  plate  machine  already  described  is 


FIG.  3. — THE 
LEYDEX  JAR 


Statical  BlectrfcftE  21 

put  in  motion  and  the  knob  of  the  jar  is  held  in 
contact  with  the  prime  conductor  of  the  machine, 
the  outer  coating  of  the  jar  being  in  electrical 
contact  with  the  earth.  It  is  quite  sufficient  that 
the  jar  is  held  in  the  hands  as  the  conductivity 
of  the  body  of  the  operator  will  be  equal  to 
the  work.  "No  sensation  will  be  experienced  in 
the  hands  or  body  while  this  work  is  in  progress. 

The  intensity  of  the  charge  that  a  Leyden  jar 
is  capable  of  receiving  depends  upon  the  extent 
of  the  surface  of  the  coating  and  the  distance  be- 
tween the  nearest  points  of  metallic  or  electrical 
contact  between  the  inner  and  outer  coatings. 
The  greater  the  surface  of  the  coatings  the  more 
intense  can  the  charge  be  made.  If  the  charge 
be  made  too  great  for  the  capacity  of  the  jar  a 
spark  will  leap  through  the  air  across  the  interval 
between  the  coatings  and  the  charge  will  in- 
stantly disappear. 

"Where  it  is  desired  to  store  a  very  intense 
charge  several  Leyden  jars  may  be  used  together 
in  a  battery.  The  ordinary  method  of  forming 
such  a  battery  is  to  place  the  desired  number  of 
jars  together  in  a  box  with  their  outer  coatings 
in  metallic  contact  with  each  other  and  the  earth. 
The  inner  coatings  are  also  electrically  connected 
by  a  metallic  circuit.  The  whole  battery  may 


22 

then  be  charged  in  the  same  manner  as  a  single 
jar.  For  convenience  a  metallic  rod  having  a 
ball  at  each  end  and  a  glass  or  insulated  handle 
is  used  to  carry  the  charge  from  the  prime  con- 
ductor of  the  plate  machine  to  the  battery.  In 
this  way  a  charge  can  be  stored  that  will  leap 
across  many  inches  of  space. 

There  are  a  few  precautions  that  should  be 
taken  in  the  making  and  operation  of  .Ley den 
jars,  in  order  that  satisfactory  results  may  be 
obtained. 

In  the  first  place  a  good  quality  of  glass,  that 
is  free  from  air  holes,  distortions  and  defects 
should  be  used.  A  poor  quality  of  glass  is  likely 
to  be  perforated  by  even  moderate  charges,  and 
then  the  jar  will  be  useless,  for  the  charge  will 
pass  directly  through  to  the  outer  coating  and  be 
dissipated  on  the  earth.  But  even  when  the  best 
quality  of  glass  is  used  an  over-charge  may 
pierce  the  glass.  As  already  stated  the  differ- 
ence between  a  conductor  and  a  non-conductor  is 
a  difference  in  the  resistance  which  they  offer  to 
the  passage  of  an  electrical  current.  Glass,  for 
example,  is  called  a  non-conductor  because  the 
resistance  offered  by  it  to  the  electrical  current 
is  very  high. 

The  passage  of   a  current  through   any  con- 


Statical  Electricity  23 

ductor  causes  heat  and  the  greater  the  re- 
sistance offered  the  higher  will  be  the  tempera- 
ture produced.  So,  when  a  charge  in  a  Leyden 
jar  is  sufficiently  intense  to  cause  it  to  pierce  the 
glass,  the  resistance  offered  by  the  latter  pro- 
duces so  high  a  local  temperature  that  the  un- 
equal expansion  of  that  and  the  surrounding 
parts  causes  a  rupture  to  take  place. 

This  same  resistance  and  the  resulting  eleva- 
tion of  temperature  is  what  causes  a  stroke  of 
lightning  to  set  fire  to  a  building  or  char  the 
body  of  a  man  or  animal  that  is  struck. 

With  a  well  constructed  battery  of  Leyden 
jars,  the  spark  or  discharge  may  be  made  to  leap 
across  many  inches  of  space  intervening  between 
the  points  in  contact  with  the  inner  and  outer 
coatings  of  the  jars.  Observation  has  shown 
that  this  spark  possesses  the  same  characteristics 
that  have  been  observed  in  a  flash  of  lightning. 
That  is  to  say,  it  apparently  follows  a  zigzag 
course  with  sharp  angles  between  the  straight 
lines.  The  duration  of  such  a  spark  is  exceed- 
ingly short.  Just  what  its  actual  duration  is  has 
not  been  determined  with  an  accuracy  that  is  ac- 
cepted as  final.  It  has  been  shown,  however, 
that  the  discharging  spark  from  a  Leyden 
jar  lasts  less  than  Tsfav  of  a  second  and  it 


24  Electricity 

is   very  probable  that  it  lasts  less  than 
part. 

In  the  charging  and  discharging  of  Leyden 
jars  great  caution  should  be  exercised  that  the 
discharge  does  not  pass  through  the  body.  In 
the  cases  of  small  jars  no  physical  injury  will 
probably  result  from  such  an  occurrence.  The 
only  effect  will  be  the  sudden  shock  and  twitch- 
ing of  the  muscles  through  which  the  discharge 
takes  place.  In  the  case  of  a  large  battery,  how- 
ever, that  is  capable  of  causing  a  spark  to  leap 
across  an  interval  of  from  six  inches  to  eight 
inches,  the  effect  of  passing  it  through  the  body 
may  be  fatal.  Such  shocks  should  be  especially 
avoided  by  all  persons  who  have  weak  hearts. 

The  Leyden  jar  cannot  be  used  for  ordinary 
electrical  operations  such  as  the  driving  of 
motors,  the  ringing  of  bells  and  other  work  of  a 
similar  character.  Its  feature  is  that  it  instantly 
discharges  itself  and  becomes  perfectly  inert  the 
moment  the  spark  or  charge  is  allowed  to  leap 
across  the  interval  separating  the  inner  from  the 
outer  coating.  This  statement  needs,  however, 
a  slight  modification. 

If  the  jar  is  allowed  to  stand  for  a  few  mo- 
ments after  the  discharge,  it  will  be  found  that 
another,  but  very  much  fainter  discharge  can  b0 


Statical  Electrtctts  25 

obtained.  This  is  due  to  the  fact  that  the  main 
discharge  has  taken  place  in  such  an  inconceiv- 
ably short  interval  of  time  that  the  whole  charge 
has  not  had  time  to  reach  the  discharging  point 
before  the  resistance  of  the  air  interval  becomes 
too  great  to  allow  it  to  pass.  The  remainder 
therefore  spreads  itself  out  over  the  coating  and 
is  ready  to  produce  a  smaller  and  much  weaker 
discharge.  This  may  sometimes  be  repeated 
several  times,  in  the  case  of  large  and  powerful 
batteries,  each  succeeding  discharge  becoming 
weaker  than  the  preceding.  Such  charges  are 
known  as  residual  charges. 

As  the  discharge  of  a  Ley  den  jar  may  take 
place  through  the  glass  of  the  jar  itself,  so  the 
discharging  spark  may  be  made  to  pierce  and 
perforate  any  non-conducting  material  placed  be- 
tween the  discharging  points.  As  the  spark 
leaps  across  the  interval  it  comes  into  contact 
with  this  material  of  high  resistance  and  instantly 
enough  heat  is  generated  to  burn  a  hole  through 
the  substance  thus  interposed.  In  this  case,  too, 
the  fractures  resemble  those  of  lightning  on  a 
smaller  scale. 


CHAPTER  III 

CONDUCTORS,    CONNECTIONS,  INSULATION    AND 
BATTERIES 

IT  has  already  been  explained  in  a  previous 
chapter  that  all  substances  will  conduct  electric- 
ity but  with  very  different  degrees  of  resistance. 
Where  it  is  desired  to  conduct  an  electric  current 
from  one  point  to  another  a  material  that  offers 
a  low  resistance  to  the  passage  of  the  current  is 
used.  Silver  is  probably  the  best  material  for 
electric  conductors  and  it  is  sometimes  used  on 
very  delicate  and  expensive  instruments ;  but  it 
is  too  costly  for  ordinary  commercial  use.  Cop- 
per stands  so  high  upon  the  list  of  good  conduc- 
tors that  it  is  very  extensively  employed. 
Where  the  cost  of  this  metal  is  too  great,  iron  is 
used. 

Where  it  is  impossible  or  undesirable  to  use  a 
single  unbroken  piece  of  metal  throughout  the 
whole  distance  over  which  it  is  desired  to  carry 
the  current  or  charge,  several  pieces  may  be 
used.  When  this  is  done  care  should  be  taken 

26 


Conductors,  Connections  27 

in  connecting  one  of  these  pieces  with  the  other, 
to  see  that  the  contact  between  them  is  intimate 
and  metal  to  metal  so  that  the  resistance  to  the 
passage  of  the  current  may  be  reduced  to  a  mini- 
mum. This  union  may  be  effected  in  several 
ways.  Fig.  4  shows  the  simplest  and  easiest 
method  of  do- 
ing this  work. 
The  wires  FIG.  4.— THE  AMERICAN  TELEGEAPH 
should  first  be  SPLICE 

scraped  until  they  are  bright  and  then  be  brought 
together  and  tightly  twisted.  This  insures  several 
points  of  actual  metallic  contact  so  that  when 
well  made  there  is  little  or  no  loss  of  energy  in 
the  transmission  of  the  current  through  the 
wire. 

Other  and  more  troublesome  methods  consist 
in  bringing  the  two  ends  together  and  either 
soldering  or  brazing  them.  This  need  only  be 
done  where  very  large  conductors  are  used, 
where  heavy  currents  are  to  be  transmitted  or 
where  it  is  necessary  to  economize  in  space  and 
it  is  undesirable  to  increase  the  diameter  of  the 
wire. 

In  laying  a  conductor  for  the  transmission  of  a 
current,  great  care  should  be  taken  to  see  that  it 
is  properly  insulated.  If  the  earth  is  used  for 


28  BlectrtcftE 

the  return  current  the  wire  should  be  separated 
from  it  by  some  good  non-conductor  or  an  air 
space  of  such  width  that  the  current  cannot  leap 
across  the  space  or  gap. 

As  to  the  materials  to  be  used  it  may  be  taken 
that  copper  is  the  metal  to  be  used  under  ordi- 
nary conditions.  This  includes  all  house  and 
outdoor  wiring  for  usual  distances.  For  long 
distance  work,  iron  may  be  used  to  save  expense 
but  copper  is  rapidly  coming  in  for  even  this 
purpose  on  account  of  the  greater  efficiency  and 
decreased  cost  of  operation. 

In  regard  to  insulation,  for  a  bare  wire,  a  glass 
or  porcelain  support  should  be  used.  For  small 
work  these  supports  can  be  screwed  to  any  part 
of  the  wall.  The  fastening  should,  however,  be 
secure  and  strong  so  as  to  insure  the  insulator 

against  being  torn 
away  by  the  ten- 
sion of  the  wire. 
A  convenient 
FIG.  5.— WIEE  AND  INSULATOR  method  is  shown 

in   Fig.    5.      This 

consists  in  laying  the  main  wire  up  against 
the  insulator  and  binding  it  there  by  a  short 
length  of  wire  twisted  about  it  at  either  side  as 
shown.  The  main  wire  may  also  be  passed 


Conductors,  Connections  29 

around  the  insulator  so  as  to  form  its  own  fasten- 
ing. In  any  case  the  main  wire  should  be  drawn 
taut  so  that  the  sag  is  reduced  to  a  minimum. 
The  wire  must  never  be  allowed  to  sag  so  that  it 
will  touch  anything  outside  the  conductors. 

The  difficulty  of  running  bare  wires  along 
walls  and  ceilings  for  interior  work  is  such  that 
it  is  never  used  for  that  purpose.  Insulated  wire 
is  invariably  used.  This  consists  of  a  copper  wire 
covered  for  its  whole  length  with  some  flexible 
insulating  material.  There  are  various  composi- 
tions used  for  this  purpose  adapted  to  different 
classes  of  work.  For  ordinary  interior  work 
such  as  bell,  telegraph  and  telephone  work,  a 
copper  wire  insulated  with  a  wrapping  of  cotton 
thread  dipped  in  parafine  is  used,  with  a  coating 
of  parafine  on  the  outside  to  protect  the  whole 
from  moisture.  For  electric  lighting  work,  the 
insulation  is  usually  of  some  rubber  or  asphalt 
composition  that  is  thicker  than  the  cotton  wind- 
ing and  less  flexible  but  still  sufficiently  so  to 
permit  of  easy  adjustment. 

The  fastening  of  insulated  wires  is  less  difficult 
than  where  bare  wires  are  used.  For  light 
wires  or  where  the  service  is  to  be  but  tempo- 
rary and  only  light  currents  are  to  be  used,  the 
cotton-wrapped  wires  may  be  attached  to  the 


so  jElectrfcftB 

partition  or  wall  by  means  of  ordinary  double* 
pointed  tacks.  When  this  method  is  pursued 
care  should  be  taken  that  the  tack  straddles  the 
wire,  that  it  does  not  cut  into  the  insulation  on 
either  side  and  that  it  is  not  driven  home  so  tightly 
as  to  cut  into  the  insulation  from  the  top.  If 
this  is  done  the  metal  of  the  tack  will  be  apt  to 
come  into  contact  with  the  copper  of  the  wire 
and  short-circuiting  be  the  result.  Such  short 
circuits  are  exceedingly  difficult  to  locate  and 
should  therefore  be  avoided  in  the  stringing  of 
the  wire  in  the  first  place. 

The  term  short-circuiting  is  used  to  express 
the  fact  that  the  current  takes  a  shorter  circuit 
from  one  pole  of  the  battery  to  the  other.  It 
will  always  follow  the  path  of  least  resistance  and 
if  there  is  any  way  by  which  it  can  get  across 
from  the  outgoing  to  the  return  wire  without 
traversing  the  whole  length  of  the  circuit  it  will 
do  so.  Hence  any  breakage  of  the  insulation 
that  puts  the  two  wires  in  contact  with  each 
other  will  cause  a  short  circuit  and  cut  the  cur- 
rent off  from  the  point  where  it  was  intended 
that  it  should  do  its  work. 

Under  no  circumstances  should  an  attempt  be 
made  to  hold  two  wires  beneath  one  and  the 
same  tack.  They  will  be  almost  certain  to  be 


Conductors,  Connections  31 

crowded  together  at  some  point  and  cause  a 
great  deal  of  annoyance  by  the  short-circuiting 
that  will  result.  Always  string  each  wire  of  a 
circuit  separately  if  it  is  desired  to  avoid  such 
annoyances. 

It  is  understood  that  by  a  circuit  is  meant 
the  line  of  wire  or  electrical  connections  extend- 
ing from  one  pole  of  a  battery  to  the  other  and 
thence  through  the  battery  to  the  original  pole. 

This  method  would  not  be  allowed  by  the  fire 
underwriters  for  electric  lighting  work.     Here 
the  insulated  wires  are  themselves  held  to  or 
clamped  between    other    in- 
sulators.    A  common  method 
is  to  hold  the  wire  clamped 
between  two  grooved  pieces 
of  wood  as  shown  in  Fig.  6.    Fia.     6.— HOLDING 
The  upper  piece  rests  against      CLAMPS  FOB  INSU- 
the  wall  or  ceiling  and  one  or      LATED  WmES 
two  screws  can  be  made  to  hold  the  whole  in 
position.     Fig.  6  shows  the  clamp  holding  two 
wires ;  the  outgoing  and  the  return. 

When  a  length  of  wire  has  been  used  and  it  is 
necessary  to  couple  on  another  length,  the  work 
can  be  done  in  practically  the  same  manner  as 
with  the  bare  wire  as  shown  in  Fig.  4.  The 
insulation  is  to  be  cut  away  for  a  distance  back 


32  jeiectricftg 

from  the  ends  of  the  wires  to  be  joined  and  they 
are  to  be  scraped  bright  and  free  from  all  oxidi- 
zation. They  are  then  t \visted  together,  after 
which  the  bare  portion  should  be  tightly  wrapped 
with  adhesive  insulating  tape.  The  job  will  be 
improved  if  the  joint  is  soldered  or  brazed  before 
being  wrapped.  The  object  is  to  make  such  a 
joint  that  its  conductivity  is  equal  to  that  of  the 
uncut  wire.  This  avoids  all  danger  of  sparking 
and  heating.  If  this  should  occur  the  insulation 
would  be  apt  to  take  fire  and  a  disaster  be  the 
result.  Many  serious  fires  have  occurred  because 
of  the  failure  to  pay  attention  to  these  little  de- 
tails in  the  original  stringing  of  the  wires. 

In  addition  to  the  important  element  of  the 
conductor  for  the  conveyance  of  the  current 
from  one  point  to  another,  we  have  the  other 
still  more  important  one  of  the  generation  of  the 
electric  current  to  be  carried.  We  have  already 
seen  how  an  electric  charge  that  may  be  stored 
in  a  Leyden  jar  may  be  developed  by  the  rubbing 
of  a  glass  plate.  But  this  statical  form  of  elec- 
tricity disappears  on  the  instant  of  the  closing  of 
the  circuit  leaving  the  parts  inert  and  dead. 

Where  there  is  to  be  a  continuous  manifes- 
tation of  electrical  energy  there  must,  therefore, 
be  a  continuous  development  or  generation  of 


Conductors,  Connections  33 

the  current.  At  the  present  time  this  is  accom- 
plished in  two  ways,  by  the  use  of  a  battery  or  a 
dynamo.  The  former  is  used  where  small  quan- 
tities and  low  voltages  (a  term  that  will  be  ex- 
plained later)  are  required,  and  the  latter  where 
the  conditions  are  reversed,  at  least  so  far  as 
quantity  is  concerned,  though  the  voltage  may 
still  be  low. 

For  such  work — then — as  the  ringing  of  bells, 
the  local  work  of  the  electric  telegraph  and  tele- 
phone, the  operation  of  signals  and  the  like,  a 
battery  of  some  form  is  used.  It  is  less  expen- 
sive to  install  and  as  it  does  not  require  the  con- 
stant attention  that  a  dynamo  does,  it  is  more 
economical  to  operate. 

A  battery  may  be  defined  as  an  "  apparatus 
arranged  to  produce  a  continuous  flow  of  an 
electric  current." 

The  forms  which  this  battery  may  be  and  have 
been  made  to  take  are  innumerable ;  but  only  a 
few  of  the  more  common  forms  that  are  easily 
made  will  be  taken  up. . 

The  strength  of  a  battery  may  be  said  to  be 
almost  exactly  proportional  to  the  number  of 
cells  or  elements  of  which  it  is  composed.  The 
work  to  be  done  will,  therefore,  determine  the 
number  of  cells  to  be  employed.  For  example, 


34  Electricity 

it  is  evident  that  more  power  is  required  to 
operate  the  hammer  of  an  electric  bell  than  to 
move  the  armature  of  an  electric  telegraph  in- 
strument. Therefore,  with  the  same  length  of 
wire,  it  may  be  assumed  that  more  cells  of 
battery  will  be  required  in  the  one  case  than  in 
the  other. 

Batteries  may  be  broadly  divided  into  two 
general  classes,  the  wet  and  the  dry.  The  former 
have  the  advantage  of  being  more  reliable  in  the 
development  of  the  current,  more  constant  in 
operation  and  more  easily  replenished  and  are, 
therefore,  almost  universally  used  when  the 
battery  can  be  placed  in  some  stationary  position 
where  it  is  not  likely  to  be  disturbed.  The  dry 
battery,  on  the  other  hand,  possesses  the  very  im- 
portant advantage  of  being  readily  transported 
from  place  to  place,  of  having  no  liquid  to  be 
spilled  by  shocks  or  jars  and  of  working  in  any 
desired  position. 

Of  the  wet  batteries  the  Daniell's  cell  is  one  of 
the  easiest  to  construct  and  most  efficient  in 
operation.  It  was  first  brought  out  in  1836  and 
is  named  after  its  inventor.  It  has  been  im- 
proved from  time  to  time  and  has  now  reached  a 
high  degree  of  perfection. 

The  general  appearance  of  a  battery  composed 


Conductors,  Connections 


35 


of  four  cells  is  shown  in  Fig.  7.  It  consists  of 
four  cells  with  the  positive  pole  of  one  connected 
with  the  negative  pole  of  the  next  and  in  such  a 
way  that  the  current  passes  from  one  to  another 
until  it  reaches  the  last  whence  it  flows  out  on  to 
the  line.  Each  cell  is  made  up  of  six  parts,  an 


FIG.  7.— BATTERY  OF  DANIELL  CELLS  AND  BELL 
CIRCUIT 

outside  containing  jar  of  glass  in  which  there  is 
set  down  a  thin  hollow  cylinder  of  zinc.  Within 
this  there  is  a  porous  porcelain  jar  and  within 
this  a  strip  of  copper.  There  are  also  two  liquids 
used.  A  saturated  solution  of  the  sulphate  of 
copper  is  placed  in  the  porous  jar  and  in  the 


36 

outer  one  there  is  diluted  sulphuric  acid.  The 
porosity  of  the  porcelain  jar  permits  the  two 
liquids  to  communicate  and  thus  form  the  con- 
necting link  for  the  generation  and  passage  of 
the  current. 

In  the  making  of  such  a  cell  care  should  be  ex- 
ercised in  the  selection  of  the  materials  used. 
The  glass  for  the  outer  jar  should  be  of  first- 
class  quality  else  it  will  be  apt  to  crack  and 
allow  the  acid  contents  to  leak  out  upon  sur- 
rounding objects. 

The  porous  jars  are  usually  made  of  porcelain 
or  earthenware  as  these  are  less  easily  affected 
by  the  acid  than  other  substances,  although  it  is 
quite  possible  to  secure  a  satisfactory  efficiency 
by  the  use  of  paper  pulp,  canvas,  pipe  clay, 
wood  or  carbon,  or  in  fact  any  material  that  is 
not  directly  and  rapidly  acted  upon  by  the 
liquids. 

It  has  been  found  that  a  variation  of  the 
amount  of  porosity  in  a  jar  has  little  or  no  effect 
upon  the  action  of  the  cell  as  far  as  resistance  is 
concerned.  In  consequence  of  this,  experiments 
seem  to  point  to  the  desirability  of  using  rather 
dense  than  openly  porous  jars  for  batteries  that 
are  to  be  kept  in  continual  operation. 

Before  using,  these  jars  should  be  soaked  in 


Conductors,  Connections  37 

water  for  some  time  so  that  the  pores  may  be- 
come thoroughly  filled  with  moisture.  If  this  is 
inconvenient,  the  jar  may  be  placed  in  position 
and  allowed  to  stand  for  a  time  before  the  bat- 
tery is  put  into  action  in  order  to  allow  the 
porcelain  to  become  saturated. 

The  use  of  jars  that  are  too  porous  should  be 
avoided  because  they  permit  the  liquids  to  mingle 
too  easily,  which  will  allow  the  zinc  to  act 
directly  upon  the  sulphate  of  copper  and  thus 
cause  a  deposit  of  copper  to  form  upon  the  zinc 
thereby  checking  the  action  of  the  cell. 

In  the  preparation  of  the  liquids  the  sulphate 
of  copper  is  obtained  by  placing  a  crystallized 
sulphate  of  copper  commonly  known  as  blue- 
vitriol  in  water  and  allowing  it  to  stand  until 
the  crystals  cease  to  diminish  in  size  when  the 
solution  will  be  found  to  be  saturated.  That  is 
to  say  the  water  has  taken  up  all  that  it  is 
capable  of  dissolving.  The  liquid  can  then  be 
poured  off  and  used  in  the  battery.  It  is  com- 
mon practice  to  keep  a  piece  of  the  vitriol  in  the 
battery  thus  holding  the  solution  up  to  the  satu- 
ration point  at  all  times.  As  the  liquid  decreases 
in  quantity  from  evaporation  or  decomposition, 
water  can  be  added  to  bring  it  up  to  the  proper 
level  431656 


38  Blectrfcttg 

The  sulphuric  acid  is  merely  diluted  with 
about  twelve  times  its  own  weight  of  water. 
Care  must  be  exercised  in  doing  this  that  it  is 
not  done  too  suddenly  or  in  a  vessel  of  inferior 
character.  The  addition  of  the  water  to  the 
acid  is  always  accompanied  by  the  development 
of  a  considerable  amount  of  heat  that  will  be  apt 
to  crack  or  burst  a  vessel  made  of  cheap  glass. 
The  safe  way  for  the  inexperienced  person  is  to 
add  the  water  slowly,  stirring  it  in  and  using 
glazed  earthenware  for  the  mixing  vessel. 

There  is  one  fault  connected  with  the  DanielPs 
cell  that  is  apt  to  cause  considerable  anno}Tance 
when  it  is  placed  in  a  position  where  cleanliness 
is  especially  desirable.  This  is  what  is  known  as 
the  formation  of  "  climbing  salts." 

The  action  of  the  battery  consists,  in  part,  in 
the  dissolving  of  the  zinc  in  the  sulphuric  acid 
and  the  formation  of  the  sulphate  of  zinc.  As 
the  liquid  becomes  saturated  with  this  sulphate. 
of  zinc,  the  climbing  salts  appear.  They  consist 
of  a  white  salt-like  deposit  on  the  surface  of  the 
glass  and  may  rise  and  overrun  the  whole  of  the 
outside  and  all  of  the  connections.  The  climb- 
ing is  caused  first  by  some  movement  produc- 
ing a  wave  in  the  liquid  and  wetting  the  glass 
above  the  general  level.  This  liquid  drys  and 


Conductors,  Connections  39 

leaves  a  deposit  upon  the  glass.  Capillary  at- 
traction then  sets  in  and  the  liquid  is  drawn  up 
to  evaporate  and  increase  the  deposit. 

In  one  way  these  deposits  are  of  an  advantage 
in  the  working  of  the  battery  in  that  they  pre- 
vent a  too  great  concentration  of  the  liquid  and 
a  depositing  of  the  salts  on  the  surface  of  the 
zinc,  both  of  which  tend  to  increase  the  resist- 
ance of  the  battery  as  well  as  lower  its  effi- 
ciency. 

These  salts  are  easily  detached  from  the  glass 
by  wiping  with  a  rag,  but  when  they  accumulate 
on  the  porous  jar  it  may  take  considerable  rub- 
bing to  remove  them.  For  this  reason  that 
portion  which  rises  above  the  surface  of  the 
liquid  should  be  glazed.  When  removed  the 
salts  should  not  be  put  back  in  the  liquid  as  that 
would  merely  intensify  the  evil.  When  the  bat- 
tery is  placed  in  an  accessible  position  it  can  be 
easily  kept  clean. 

The  formation  of  climbing  salts  can  be  pre- 
vented by  placing  a  layer  of  oil  on  top  of  the 
liquid.  This  is  apt  to  foul  the  battery,  however, 
and  to  add  to  the  concentration  of  the  outer 
liquid,  thus  raising  the  resistance  and  with  it 
lowering  the  efficiency  of  the  battery.  They 
can,  however,  be  prevented  from  climbing  over 


40  jeiectrtcfts 

and  passing  beyond  the  limits  of  the  edge  of  the 
jar  by  coating  the  upper  portion  of  the  same 
with  a  film  of  oil  or  paraffine. 

In  the  wiring  of  the  cells  of  a  battery  the 
work  should  be  done  as  indicated  in  Fig.  7.  A 
wire  is  led  from  the  zinc  of  one  cell  to  the  copper 
of  the  next,  from  the  first  to  the  last  and  thence 
back  to  the  first.  The  metals  should  be  sus- 
pended in  the  liquid  from  a  rack  set  on  top  of 
the  jars  and  not  allowed  to  rest  on  the  bottom 
of  the  same.  These  racks  may  be  made  of  wood 
or  of  hard  rubber.  The  porous  jar  should  also 
be  suspended. 

Each  metal  should  be  provided  with  a  binding 
screw  for  the  attachment  of  the  wires.  This 
consists  of  a  threaded  bolt  soldered  or  brazed  to 
the  zinc  and  copper  and  provided  with  a  knurled 
nut  that  may  be  screwed  down  against  a  bearing 
to  hold  the  wire. 

Whenever  it  becomes  necessary  to  remove  the 
wires  for  the  purpose  of  cleaning  the  battery, 
they  and  the  nut  and  bearing  should  be  scraped 
bright  so  as  to  insure  a  metallic  contact  before 
replacing. 

In  the  care  of  the  battery  it  will  be  necessary 
to  add  a  little  water  from  time  to  time  to  re- 
place that  lost  by  evaporation.  Otherwise  it 


Conductors,  Connections  41 

will  require  no  attention  other  than  the  removal 
of  the  salts  until  it  has  become  exhausted. 

The  life  of  a  battery  depends  upon  the  service 
which  it  is  called  upon  to  perform.  In  telegraph 
service,  where  the  battery  is  almost  constantly 
at  work,  it  will  be  six  months  or  a  year  before 
the  porous  jars  will  become  so  clogged  with  a 
metallic  deposit  as  to  require  renewal. 

For  household  purposes,  such  as  the  ringing  of 
bells,  the  service  is  intermittent  and  the  battery 
stands  with  an  open  circuit  for  the  greater  por- 
tion of  the  time,  its  life  may  be  almost  indefi- 
nitely extended. 

In  connecting  the  battery  to  the  instrument 
intended  to  do  the  work  the  wiring  is  very 
simple.  A  conductor  is  attached  to  the  binding 
post  of  the  zinc  at  one  end  of  the  battery,  which 
is  known  as  the  negative  pole ;  and  one  to  that 
of  the  copper  at  the  other  end,  which  is  known 
as  the  positive  pole.  If  these  two  wires  are 
brought  together  so  as  to  complete  the  metallic 
contact  between  the  two  poles  of  the  battery, 
the  circuit  is  said  to  be  closed  and  the  current 
flows  in  the  circuit  from  the  positive  pole  to  the 
negative  and  thence  through  the  battery  to  the 
positive  pole  again. 

If  then  an  electric  bell  were  to  be  connected 


42  Electricity 

in  this  closed  circuit  it  would  ring  continuously 
until  the  battery  was  exhausted.  In  order  to 
control  the  ringing  of  the  bell  the  wire  is  broken, 
as  at  a,  and  a  push-button  or  key  inserted,  by 
which  the  circuit  can  be  opened  or  closed  at 
will.  When  closed,  the  battery  is  instantly  set  to 
work  and  the  bell  rings.  When  open,  the  bell 
is  silent  and  the  battery  is  at  rest,  suffering  no 
deterioration  other  than  that  due  to  the  evapora- 
tion of  the  liquids  in  the  jar. 

There  are,  as  already  stated,  many  forms  of  the 
Daniell's  cell,  intended  for  the  accomplishment  of 
special  purposes,  but  acting  on  the  same  principle. 
Many  of  these  batteries  have  received  a  wide  ap- 
plication and  have  supplanted  the  simple  Daniell's 
cell.  They  are,  however,  usually  more  difficult  to 
make  and  maintain  and  are,  therefore,  not  as  well 
suited  to  the  needs  of  those  who  wish  to  make 
and  care  for  their  own  batteries. 

Among  such  batteries  may  be  mentioned  the 
Leclanche.  In  this,  the  glass  jar  is  usually  square 
and  is  narrowed  in  at  the  top  so  as  to  just  per- 
mit the  removal  of  the  porous  jar  and  thus  de- 
crease the  chance  of  evaporation.  The  contrac- 
tion, however,  contains  a  side  orifice  through 
which  the  zinc  can  be  inserted  and  the  jar  filled 
and  emptied. 


Confcuctors,  Connections  43 

One  electrode  is  a  cylindrical  piece  of  zinc 
about  a  half-inch  in  diameter,  to  which  a  piece 
of  galvanized  wire  is  soldered.  The  porous 
jar  is  filled  with  a  mixture  consisting  of  equal 
parts  of  crushed  carbon  and  peroxide  of  man- 
ganese ;  while,  packed  in  the  centre  of  this  mass, 
is  a  piece  of  carbon  having  a  lead  cap  to  which 
the  positive  binding  post  is  fastened. 

The  liquid  in  the  outside  jar  consists  of  one- 
half  water  and  one-half  ammonia-hydrochlorate. 
The  liquid  soaks  through  the  porous  jar  and 
saturates  the  mixture  of  carbon  and  manganese. 

This  form  of  jar  is  well  adapted  for  working 
bells  and  doing  a  similar  class  of  work,  but 
owing  to  the  difficulty  of  making  had  best  be 
purchased  of  a  dealer  when  it  is  desired  to 
use  it. 

Finally,  a  word  of  caution  may  be  given  to  the 
unskilled  in  the  care  of  a  battery.  In  dismount- 
ing one  for  cleaning  or  renewal  it  is  well  to  have 
a  little  aqua  ammonia  within  reach,  into  which 
the  fingers  may  be  immersed  in  case  they  be- 
come spattered  with  the  acid,  or  which  may  be 
used  to  moisten  the  clothes  that  have  suffered 
from  a  similar  accident.  Always  do  this  work 
in  a  well-ventilated  room,  because  the  fumes  that 
are  apt  to  arise  from  the  acid  of  the  battery  are 


44  BlectrtcftB 

not  only  disagreeable  but  harmful  when  taken 
into  the  lungs. 

The  second  class  of  batteries  known  as  dry  are 
not  really  dry,  but  rather  moist.  In  fact  as  soon  as 
they  become  thoroughly  dried  they  cease  to  work. 
It  is  upon  this  principle  that  some  of  the  fuses  used 
for  submarine  work  operate.  So  long  as  the  pile 
is  kept  dry  there  is  no  generation  of  an  electric  cur- 
rent. When  water  is  admitted  so  as  to  moisten 
the  parts  the  electric  current  is  at  once  generated. 

These  batteries  are  so  low-priced  that  it  is  not 
worth  the  time  required  to  make  them.  If,  how- 
ever, it  is  desired  to  do  such  a  piece  of  work  it 
may  be  accomplished  as  follows : 

Take  an  unglazed  sheet  of  paper  and  upon  one 
side  of  it  spread  a  thin  layer  of  peroxide  of  man- 
ganese that  has  itself  been  thinned  with  milk, 
thin  flour  paste  or  water  containing  a  little  glue 
or  mucilage.  From  the  paper  so  prepared  cut 
discs  about  l}4  inches  in  diameter  and  stack 
them  on  top  of  each  other  to  any  convenient 
height.  At  each  end  a  metallic  disc,  preferably 
of  copper,  of  the  same  diameter,  is  placed,  and 
these  serve  to  form  the  poles  or  electrodes  of  the 
battery.  The  whole  is  then  pressed  solidly  to- 
gether and  held  in  that  position. 

In  order  that  the  outer  surface  may  be  smooth 


Conductors,  Connections  45 

and  cylindrical,  a  hole  may  be  punched  through 
the  centre  of  the  discs  and  an  insulated  wire  be 
led  from  the  bottom  up  to  the  top. 

The  whole  may  be  held  together  by  packing 
in  a  glass  tube  of  the  proper  diameter  that  has 
been  well  varnished  with  shellac  on  the  inside. 
If  a  glass  tube  is  undesirable  or  inconvenient  to 

o 

procure,  the  metallic  discs  may  be  made  a  little 
larger  than  the  paper  ones  and  pierced  around 
their  edges  with  a  number  of  small  holes. 
Through  these  holes  a  lacing  of  silk  cord  may 
be  passed  from  one  to  the  other  and  the  whole 
bound  firmly  in  place. 

As  the  action  of  such  a  pile  depends  upon  the 
retention  of  its  moisture  it  must  be  hermetically 
sealed  in  such  a  way  that  it  cannot  become  dry. 
To  do  this  it  had  best  be  given  several  coatings 
of  shellac  varnish,  paraffine  or  sulphur.  If  the 
pile  is  to  be  set  in  one  place  paraffine  will  be 
as  satisfactory  as  anything.  But  if  it  is  to  be 
handled  or  moved  about,  the  paraffine  will  be 
apt  to  become  loosened  and  scraped  off,  in  which 
case  the  shellac  should  be  used. 

While  an  electric  spark  can  be  obtained  from 
these  batteries  and  they  can  be  made  to  operate 
a  telegraph  or  other  instruments  requiring  a  light 
current  their  internal  resistance,  owing  to  the 


46  Electricity 

great  number  of  elements  is  enormous,  and  they 
are  not  adapted  to  long-continued  or  severe  service. 

They  are,  however,  exceedingly  convenient  for 
the  operation  of  experimental  apparatus  that  has 
to  be  moved  from  point  to  point. 

The  wiring  and  operation  of  these  batteries  for 
service  is  identical  with  that  of  the  wet  batteries 
previously  described. 

It  has  already  been  pointed  out  that  the  bat- 
tery is  used  in  places  where  currents  of  low  in- 
tensity to  be  used  intermittently  are  to  be  used. 
This  applies  to  the  local  batteries  of  all  telegraph 
stations,  telephones,  and  household  purposes 
where  they  are  worked  intermittently  for  ring- 
ing bells,  opening  doors  or  working  light  signals. 
For  gas  lighting  on  a  large  scale  such  as  in 
theatres,  public  halls  and  railway  stations,  where 
it  is  merely  necessary  to  produce  a  spark  at  the 
tip  of  the  burner,  the  friction  machine  is  the 
most  convenient  method  to  employ.  With  this 
a  Leyden  jar  is  first  charged  and  then  discharged 
over  a  wire  with  a  gap  at  each  burner.  In  leap- 
ing this  gap  a  spark  is  formed  which  lights  the 
escaping  gas.  This  machine  for  such  a  purpose 
is  more  convenient  than  either  a  dry  or  wet  bat- 
tery as  it  is  only  required  to  furnish  an  instan- 
taneous current  and  requires  no  attention. 


CHAPTEE  IV 

ELECTKIC    BELLS 

THE  electric  operation  of  nearly  all  signals  de- 
pends upon  the  power  of  the  electric  current  to 
convert  a  bar  of  soft  wrought  iron  into  a  magnet 
of  greater  or  less  strength.  This  is  done  by  pass- 
ing the  current  through  a  wire  wound  as  a  helix 
around  the  bar  of  iron.  So  long  as  the  current 
is  flowing  through  the  wire  the  bar  is  a  magnet 
and  acts  in  every  way  like  one ;  and,  as  soon  as 
the  current  is  cut  off  and  ceases  to  flow  the  bar 
jit  once  becomes  inert  and,  for  all  practical  pur- 
poses, manifests  no  magnetic  properties  at  all. 

The  condition  of  the  bar  while  under  the  in- 
fluence of  the  current  depends  upon  the  direction 
of  its  flow  through  the  wire  and  the  way  in  which 
the  wire  is  wound  about  the  bar.  That  is,  these 
are  the  controlling  factors  in  the  location  of  the 
north  and  south  poles  of  the  magnet  at  opposite 
ends  of  the  bar.  The  law  of  the  flow  of  the  cur- 
rent is  that  if,  in  looking  at  the  end  of  the  bar, 
the  current  appears  to  be  flowing  around  it  in 


48  BlectricttB 

the  direction  of  the  movement  of  the  hands  of 
a  watch  or  from  left  over  to  right  in  passing 
from  the  positive  to  the  negative  pole  of  the  bat- 
tery, the  south  pole  of  the  magnet,  thus  formed, 
will  be  toward  the  observer.  If  the  current  is 
made  to  flow  in  the  opposite  direction  or  from 
right  over  to  left,  the  north  pole  of  the  magnet 
will  be  toward  the  observer.  This  will  be  more 
clearly  understood  from  an  examination  of  Fig.  8. 


•!\\\\\\\T 
^ 


71 


FIG.  8.  —  COMBINATIONS  OF  ELECTRO-MAGNET  COILS 

In  this  A,  B,  C  and  D  represent  the  four  combi- 
nations possible  with  the  two  directions  of  cur- 
rent and  of  windings  respectively.  This  property 
of  magnetization  is  made  use  of  in  a  wide  variety 
of  electrical  instruments. 

Eeferring  to  A  and  B  of  Fig.  8,  it  will  be  seen 
that,  in  each  case  the  north  pole  of  the  magnet 
is  at  the  left-hand  end  of  the  bar.  The  wires 
are,  however,  wound  with  what  is  known  as  a 


Electric  JBells  49 

left  and  right-hand  coil  respectively.  But  the 
current  passes  around  the  bar  in  the  same  direc- 
tion in  each  case.  It  is  evident,  then,  from  this 
that  the  wire  can  be  coiled  about  the  bar  from 
end  to  end,  back  and  forth,  like  thread  on  a  spool 
and  still  tend  to  excite  the  same  polarity  in  a 
bar. 

In  forming  a  magnet  for  a  bell,  it  is  customary 
to  construct  one  in  the  form  of  a  horseshoe,  that 
is  one  with  the  north  and  south  poles  presented 
in  the  same  direction.  The  reason  for  this  is  that 
it  makes  it  possible  to  use  a  long  armature  or 
movable  bar  that  is  excited  to  correspond  to  the 
two  poles  of  the  magnet  presented  to  it.  In  ad- 
dition to  this,  it  is  much  more  powerful  than  one 
in  the  bar  form ;  for  the  former  will  lift  three  or 
four  times  as  much  as  the  latter  having  the  same 
weight  and  number  of  ampere  turns.  This  ex- 
pression of  ampere  turns  is  used  to  represent  the 
number  of  turns  of  wire  about  the  core  multi- 
plied by  the  number  of  amperes  passing  through 
it.  That  is  to  say,  if  a  magnet  is  surrounded  by 
twenty  turns  of  wire  through  which  a  current  of 
one  ampere  is  passing,  it  is  said  to  have  twenty 
ampere  turns.  If  the  current  is  reduced  to  one- 
half  an  ampere,  it  will  then  have  ten  ampere 
turns. 


50  BlectdcftB 

An  ampere  is  the  term  used  to  indicate  the 
quantity  or  strength  of  an  electric  current.  The 
resistance  to  this  current  as  set  up  in  the  wires  is 
measured  by  ohms  and  the  intensity  or  pressure 
of  the  current  is  measured  in  volts. 

It  is  sometimes  difficult  to  grasp  the  idea  of 
electrical  quantities  when  no  tangible  and  visible 
measurement  is  possible.  For  that  reason  the 
flow  of  an  electrical  current  is  frequently  com- 
pared to  that  of  water  in  pipes.  In  the  latter 
there  are  two  elements  that  control  the  amount 
of  water  that  can  be  delivered  by  a  pipe ;  its  size 
and  the  pressure  with  which  the  water  is  forced 
through  it.  It  is  evident  that  the  larger  the  pipe 
the  greater  the  quantity  of  water  that  can  be  made 
to  pass  through  it  when  a  given  pressure  per  square 
inch  is  applied.  It  is  also  equally  evident  that 
the  volume  of  flow  of  water  will  increase  as  the 
pressure  or  head  of  water  is  increased. 

The  analogy  holds  good  in  the  case  of  electric- 
ity. We  may  consider  the  volume  of  water  flow- 
ing through  the  pipe  as  representative  of  the 
ampere;  the  pressure  or  head  with  which  the 
water  is  forced  through  the  pipe  as  representa- 
tive of  the  volt,  and  the  frictional  resistance  of- 
fered by  the  pipe  to  the  flow  of  the  water  as 
representative  of  the  ohm  or  resistance  of  the 


Electric  mile  51 

wire  to  the  flow  of  the  electric  current  through 
the  same. 

As  it  is  necessary  to  have  a  definite  mechanical 
equivalent  for  the  work  done  by  the  electric  cur- 
rent, it  is  referred  to  what  is  known  as  the  C.  G. 
S.  mechanical  unit.  This  is  based  on  the  metric 
system  of  measurement  and  means  one  gramme 
(.1452  oz.)  lifted  through  a  distance  of  one  centi- 
meter (.3937  in.)  in  one  second.  This  was  adopted 
as  a  basis  of  measurement  by  the  International 
Electric  Congress  that  met  in  Paris  in  1881  and 
1884,  and  is  known  as  the  erg. 

These  electric  measurements  are  all  inter-re- 
lated and  based  on  certain  definite  observations. 
Thus  the  ohm  is  the  unit  of  resistance  and  is  that 
offered  by  a  column  of  pure  mercury  106  centi- 
meters (41. Y3  in.)  in  length  and  of  one  square 
centimeter  (.156  sq.  in.)  in  cross-section  at  a  tem- 
perature of  32°  Fahr.  This  resistance  is  rep- 
resented within  a  small  fraction  by  1,000,000,000 
C.  G.  S.  units  of  resistance  or  about  .024  foot 
pounds  per  minute. 

The  volt  is  the  unit  of  electro-motive  force  and 
is  equal  to  about  that  of  one  Daniell's  cell.  As 
this  is  a  variable  quantity  the  volt  is  legalized  at 
100,000,000  C.  G.  S.  units. 

The  ampere  is  the  unit  of  current  strength  or 


52  Electricity 

volume  and  is  obtained  by  dividing  the  volt  by 
the  ohm  or  the  electro-motive  force  by  the  resist- 
ance and  is,  therefore,  equal  to  rV  C.  G.  S. 

The  term  ampere-hour  is  frequently  used  and 
represents  a  current  of  one  ampere  flowing 
through  a  conductor  for  the  space  of  one  hour. 

The  meaning  of  these  technical  phrases  are 
somewhat  difficult  to  grasp,  and  the  memory 
will  be  greatly  assisted  by  referring  them  to  the 
analogy  of  water  flowing 
through  a  pipe  as  already  ex- 
plained. 

Returning  now  to  the  matter 

£^$  3 — L  in  hand,  attention  should  be 
if  I  1)1  paid,  in  the  winding  of  the  mag- 

.   9.-OBDiNAiTY  net  for  an  electric  bell,  both 

METHOD  OF  WIR-  to   the  volume   or   ampereage 

ING  FOE  ELECTEO-  of  the  current  to  be  used  and 

MAGNETS  the  probabie  resistance  of  the 

balance  of  the  circuit.  As  the  latter  increases 
so  should  the  windings  and  the  resistance  of  the 
wire  about  the  magnet  also  increase. 

The  method,  then,  to  be  adopted  in  the  making 
of  the  magnet  will  be  to  obtain  two  soft  iron 
cores  about  one-half  inch  in  diameter  and  two 
inches  long  to  which  should  be  added  three- 
eighths  of  an  inch  of  screw  thread  to  go  into  a 


jSlectrfc  JBetle  53 

cross-bar,  also  of  soft  iron  upon  which  the  two 
are  to  be  fastened  so  as  to  form  the  U-shaped 
core  as  shown  in  Fig.  9. 

Over  each  of  these  cores  N"  and  S  two  thin 
wooden  bobbins  should  be  snugly  fitted.  If 
these  are  inconvenient  to  obtain  the  cores  may 
be  heated  and  wrapped  in  successive  layers  of 
paper.  When  cooled  the  paper  will  slip  off, 
forming  a  cylindrical  core. 

The  wire  should  be  wound  on  the  outside  of 
this  core  and  in  the  direction  shown  in  Fig.  9 ; 
winding  back  and  forth  until  a  sufficient  quantity 
has  been  put  in  position.  To  do  this  properly 
about  6^  oz.  of  copper  wire  of  size  No.  24  of  the 
Birmingham  wire  gauge  should  be  used.  It  is 
essential  that  the  successive  coils  of  this  wire 
should  come  in  contact  neither  with  the  iron  core 
nor  with  each  other,  else  the  current  will  be 
short-circuited  and  the  effect  of  the  coil  nullified. 

Insulated  wire  must,  therefore,  be  used  for  this 
purpose  and  in  order  that  the  coils  may  be  as 
compact  and  as  neatly  arranged  as  possible  it  is 
best  to  use  a  wire  that  is  insulated  with  silk. 
The  ends  may  be  led  out  at  the  bottom  in  a 
groove  cut  in  the  base,  to  a  binding  post  on  the 
stand  to  which  the  magnet  is  to  be  secured.  This 
may  be  of  the  form  shown  in  Fig.  23. 


54 


BlectricttE 


Having  formed  the  magnet  there  are  two  forms 
in  which  the  bell  may  be  put.  That  is,  the  bell 
may  be  made  to  ring  continuously  so  long  as  the 
circuit  is  closed  or  it  may  be  made  to  give  a 
single  stroke  with  each  closing  and  opening  of 
the  same. 

The  continuously  ringing  bell  as  shown  in  Fig. 
10,  will  be  first  con- 
sidered. The  mag- 
net is  attached  to  the 
base,  as  shown,  by 
screws.  Just  above 
it  a  bracket  A  con- 
taining a  binding 
post  is  fastened.  To 
the  face  of  this 
bracket  there  is 

screwed   a  spring  B 
FIG.  IO.-VIBRATIXG  ELECTRIC  to  the  lower  end  of 

BELL  AND  CIRCUIT  .  .  ,     ,.  .,    . 

which  the  soft  iron 

armature  C  is  attached.  This,  in  turn,  is  ex- 
tended down  to  include  the  stem  D  which 
terminates  in  hammer  E.  To  the  back  of  the 
armature  C  there  is  also  attached  the  auxil- 
iary spring  K.  The  spring  B  is  so  adjusted  that 
when  no  current  is  passing  through  the  wire  the 
armature  stands  away  from  the  faces  of  the  mag- 


Electric  JBells  55 

net  ends  and  the  spring  K  is  pressed  up  against 
the  stop  F.  This  stop  F  should  be  fitted  with  an 
adjusting  screw  by  which  the  tension  on  the 
spring  K  can  be  increased  or  diminished  and  the 
armature  brought  into  correct  adjustment.  The 
stem  D  should  also  be  bent  to  such  a  shape  that, 
just  before  the  armature  comes  into  contact  with 
the  cores  of  the  magnet  the  hammer  should  strike 
against  the  bell. 

The  wiring  of  this  bell  is  exceedingly  simple. 
One  end  of  the  wire  forming  the  coil  of  the  mag- 
net is  led  out  and  fastened  in  the  binding  post 
H.  To  this  same  binding  post  is  also  led  the 
wire  from  the  positive  pole  of  the  battery.  This 
wire  also  connects  with  the  push  button  i. 

The  other  end  of  the  wire  of  the  magnet  coil 
is  led  out  und  fastened  to  the  binding  post  on 
the  bracket  A. 

The  negative  pole  of  the  battery  is  connected 
to  the  binding  post  G  and  this  in  turn,  by  a  wire 
to  the  stop  F. 

The  course  of  the  current  then,  when  the  cir- 
cuit is  closed,  is  from  the  positive  pole  of  the 
battery  to  the  push  button  I,  to  the  binding  post 
H,  to  and  through  the  magnet  coil  to  the  bracket 
A,  to  the  spring  B,  to  the  spring  K,  to  the  stop  F, 
to  the  binding  post  G,  to  the  negative  pole  of  the 


56  BlectrfcftB 

battery  and  then  through  the  latter  to  the  posi- 
tive pole. 

The  action  of  the  bell  in  operation  is  as  fol- 
lows : 

When  the  push  button  is  pressed  to  close  the 
circuit,  the  magnet  attracts  the  armature  and 
draws  it  to  itself,  as  it  does  so  it  draws  the  spring 
K  away  from  the  stop  F.  The  moment  these  two 
are  parted  the  circuit  is  broken  and  the  magnet 
ceases  to  attract  the  armature.  The  spring  B 
then  throws  the  armature  back  to  its  original 
position.  As  soon,  however,  as  the  spring  K 
touches  the  stop  F  the  magnet  is  again  excited 
and  attracts  the  armature.  The  hammer  is  thus 
kept  vibrating  to  and  fro  as  long  as  the  circuit 
remains  closed  at  the  push  button  I. 

Trouble  is  frequently  experienced  with  the 
failure  of  these  vibrating  continuous  bells  to 
work.  This  failure  is  usually  credited  to  the 
battery  which  may  be  in  first-class  condition. 
The  difficulty  can  usually  be  traced  to  the  mech- 
anism of  the  bell.  If  the  adjustment  at  the 
stop  F  is  not  properly  made  the  bell  will  not 
ring.  It  is  evident  that  if  the  hammer  strikes 
the  gong  before  the  spring  K  leaves  the  stop  F 
and  thus  breaks  the  circuit,  the  latter  will  not  be 
broken  at  all  and  the  magnet  will  continue  to 


Electric  WellB  57 

attract  the  armature  and  there  will  be  but  one 
stroke  given  by  the  hammer  on  the  gong. 

On  the  other  hand,  if  the  stop  F  is  drawn  so 
far  back  that  the  spring  K  does  not  touch  it 
when  the  hammer  is  thrown  back  to  its  full  ex- 
tent by  the  spring  B,  the  circuit  will  always  re- 
main open  and  there  will  be  no  possibility  of 
exciting  the  magnet.  Or  if  the  spring  K  just 
touches  the  stop  F  so  that  it  is  drawn  away  as 
soon  as  the  armature  starts  forward,  the  circuit 
will  be  broken  too  soon  before  sufficient  mo- 
mentum has  been  given  to  the  hammer  to  cause 
it  to  overcome  the  resistance  of  the  spring  B  and 
reach  the  gong. 

The  proper  adjustment  of  the  stop  F  is  ob- 
tained when  the  contact  between  it  and  the 
spring  K  ceases  just  before  the  hammer  comes 
into  contact  with  the  gong.  To  be  precise  in  the 
matter :  Suppose  the  hammer  stands  three- 
quarters  of  an  inch  from  the  gong  when  at  rest. 
The  circuit  should  be  broken  when  it  has  reached 
a  point  from  one-eighth  to  three-sixteenths  of  an 
inch  from  the  gong. 

It  is  also  necessary  to  see  to  it  that  the  points 
of  contact  between  the  stop  F  and  the  spring  K 
are  kept  bright  and  clean. 

These  bells  are   usually  placed  high  on  the 


58  Blectrfctts 

wall,  and  frequently  in  damp  and  dusty  places. 
An  accumulation  of  dust  or  rust,  however  slight, 
may  be  quite  sufficient  to  break  the  circuit  at  F 
and  hold  it  open  at  all  times.  All  of  these 
things  should  be  carefully  looked  to  before  at- 
tributing a  failure  to  work  to  the  battery,  and 
they  can  be  readily  attended  to  and  the  adjust- 
ments made  by  any  householder  without  going 
to  the  annoyance  and  delay  of  sending  for  an 
outside  electrician. 

The   remaining 
piece  of  mechanism 

^  ^_  to   be    described    in 

'tfM^fcWMfa  connection  with  the 
FIG.  11.— PUSH  BUTTON         bell  is  the  push-but- 
ton that  is  shown  in 

section  in  Fig.  11.  These  push-buttons  are  very 
simple  in  construction.  The  wires  from  the  bat- 
tery and  from  the  bell  are  led  in  as  shown.  One 
terminates  in  a  flat  spiral  spring  B  and  the  other 
in  the  flat  plate  C.  By  pressing  upon  the  porcelain 
button  A,  the  spring  is  forced  down  against  the 
plate  and  the  circuit  is  closed. 

Another  type  of  bell  operated  by  electricity  is 
the  single  stroke  bell.  That  is  to  say  when  the 
circuit  is  closed  the  hammer  is  thrown  down 
against  the  gong  and  strikes  a  single  blow,  re- 


Electric  ffietls 


59 


maining  in  that  position  until  the  circuit  is 
again  opened,  to  repeat  the  blow  upon  closing 
again. 

The  construction  of  such  a  bell  is  similar  to 
that  of  the  vibrating  bell.  The  difference  is  in 
the  method  of  wiring.  A  bell  of  this  character 
is  shown  in  Fig.  12.  The  wires  from  the  coil  of 
the  magnet  are  led  off  to  the  two  binding  posts 


FIG.  12. — SINGLE  STROKE  ELECTRIC  BELL 

A  and  B  from  which  the  wires  are  led  to  the  bat 
tery  in  exactly  the  same  manner  as  in  the  bell 
shown  in  Fig.  10.  The  armature  F,  to  which  the 
stem  and  hammer  are  attached  is  held  by  the 
spring  E.  There  is,  however,  no  auxiliary 
spring  but  the  screw  D,  of  the  stop  C  is  brought 
to  bear  directly  against  the  armature  and  pre- 
vents it  from,  being  thrown  too  far  back  away 


60  ^electricity 

from  the  core  of  the  magnet.  Neither  does  the 
armature  form  any  part  of  the  electric  circuit  by 
which  the  bell  is  operated;  From  this  it  will  be 
seen  that,  when  the  cores  are  magnetized  by  the 
passage  of  the  current  the  armature  is  drawn 
forward  once  and  held  until  released  by  the 
opening  of  the  circuit. 

The  adjustments  to  be  made  for  the  operation 
of  this  bell  are  as  follows :  The  armature  should 
come  up  against  a  stop,  as  at  G  just  before  the 
hammer  strikes  the  gong.  The  momentum  of 
the  former  will  then  cause  it  to  be  thrown  ahead 
to  deliver  a  quick  blow  and  then  spring  back 
clear  of  the  gong  to  permit  the  latter  to  vibrate 
as  would  not  be  the  case  were  the  hammer  to  be 
held  in  contact. 

'  If  desired,  the  stop  G  can  be  dispensed  with  in 
the  making  of  the  bell,  and  the  armature  be  al- 
lowed to  strike  directly  against  the  core  of  the 
magnet  instead.  When  this  is  done  the  armature 
or  the  ends  of  the  cores  should  be  given  a  coat- 
ing of  copper  plating,  to  prevent  sticking.  Or, 
if  the  plating  is  inconvenient,  a  piece  of  thin 
copper  may  be  interposed. 

The  reason  for  the  sticking  is  that,  after  the 
circuit  by  which  the  core  is  magnetized  has  been 
broken,  there  will  still  remain  enough  residual 


JElectrtc  Bells  61 

magnetism  to  hold  the  armature  and  prevent  a 
quick  reaction.  For  this  reason  the  armatures  of 
bells  and  telegraph  instruments  are  not  allowed 
to  come  into  contact  with  the  cores  but  have 
their  forward  motion  checked  by  an  adjustable 
stop  with  a  screw,  like  that  shown  in  Fig.  12. 

In  fitting  up  an  electric  call  bell,  either  of  the 
vibrating  or  single  stroke  type,  the  error  is  fre- 
quently made  of  attempting  to  economize  in  the 
number  of  cells  that  are  put  into  the  battery. 
This  false  economy  will  invariably  result  in  an 
amount  of  annoyance  that  will  far  more  than 
offset  any  small  saving  that  may  be  effected.  If 
any  mistake  is  to  be  made  in  this  regard  let  it 
be,  by  all  means,  on  the  side  of  providing  more 
battery  power  than  is  really  needed.  This  power 
will  depend,  of  course,  upon  the  size  of  the  gong 
in  the  bell  to  be  operated,  because,  the  larger  the 
gong  the  greater  the  length  of  wire  in  the  mag- 
nets, and  with  it  the  greater  the  resistance. 
Then,  too,  while  the  making  of  the  core  for  the 
single  stroke  bell  is  the  same  as  for  the  vibrat- 
ing, the  size  of  the  core  and  the  quantity  of  wire 
needed  should  be  greater.  Thus  the  magnet  de- 
scribed in  the  early  part  of  this  chapter  is  suited 
for  a  vibrating  bell  with  a  gong  4  inches  in 
diameter.  For  a  similar  single  stroke  bell  the 


63  Electricity 

core  should  be  lengthened  to  2^  inches  and  tl\ 
amount  of  wire  used  increased  to  9^  oz.  For  a 
smaller  gong  of  2^  inches  diameter  the  cores 
may  be  ^  inch  in  diameter  and  1^  inches 
long,  upon  which  3  ounces  and  3^  ounces  of 
wire  respectively  should  be  wound  for  the  two 
types  of  bells. 

Two  cells  of  battery  can  be  made  to  work  such 
bells,  but  it  will  be  found  to  be  far  better  to 
allow  an  ample  margin  and  put  in  three  cells  for 
the  small  bell  and  four  for  the  large,  increasing 
this  to  six  in  case  the  circuit  is  long  or  several 
bells  are  to  be  operated.  Where  the 
work  done  is  constant  and  heavy, 
even  a  larger  number  of  cells  will  be 
advisable,  in  order  to  prevent  a 
rapid  deterioration  and  exhaustion 
FIG.  13.— SIM-  of  the  battery. 
PLEBELLCIB-  The  arrangement  of  the  cells  may 

CUIT  ,          j-     ••!     j     •     A  U    A    •       1 

be  divided  into  what  is  known  as 
multiple  and  series.  For  the  working  of  a 
single  bell  or  for  bells  that  are  used  infre- 
quently, the  series  arrangement  should  be  used. 
The  disposition  of  the  battery  of  three  cells 
and  the  wiring  for  a  single  bell,  is  shown  in 
Fig.  13.  The  three  cells  of  the  battery  are  rep- 
resented by  the  lines  at  A,  B  and  C.  These 


Electric  JBells  63 

.cells  are  said  to  be  in  series.  That  is  the  current 
passes  through  the  series  of  the  three,  one  after 
the  other.  This  arrangement  increases  the  ten- 
sion or  voltage  of  the  current  above  that  of  the 
single  cell. 

Should  the  service  on  the  line  be  constant  or 
increased  by  the  addition  of  more  bells,  the 
quantity  or  ampereage  of  electricity  may  be  in- 
creased while  the  voltage  remains 
the  same  by  adding  more  cells  and 
arranging  them  in  multiple  series. 
This  is  shown  in  Fig.  14.  Here,  it 
will  be  seen,  the  positive  poles  at 
one  end  of  each  series  of  cells,  are 
united  ;  and  the  same  is  done  for  pIG  H.—B 
the  negative  poles  at  the  other  end.  CIRCUIT  WITH 
These  two  wires  are  then  united  BATTERIES  IN 
through  the  circuit.  The  voltage  is  PARALLEL 
the  same  as  in  Fig.  13,  but  the  ampereage  is 
doubled. 

When  there  is  but  a  single  bell  worked  by  a 
single  battery  and  rung  from  a  single  push 
button,  the  wiring  should  be  done  as  shown  in 
Fig.  13.  It  is,  however,  frequently  desirable  to 
ring  one  bell  from  two  different  rooms ;  or,  it 
may  be  desired  to  ring  bells  separated  from  each 
other  from  push  buttons  located  at  one  point. 


64  Electricity 

The  latter  occurs  in  the  case  of  apartment  houses 
where  the  call  bells  are  rung  in  each  separate 
apartment  from  the  street  door. 

There  is  one  simple  principle  underlying  the 
wiring  for  bells  that  must  always  be  borne  in 
mind.  It  is  that  the  circuit  from  the  battery 
to  the  bell  must  be  unbroken  except  at  the  par- 
ticular push  button  by  which  it 
is  to  be  operated,  and  that, 
when  the  latter  is  closed,  the 
current  must  flow  direct  to  the 
FIG.  15.—  BELL  CIR-  point  of  application  and  not  be 
CUIT  WITH  Two  liable  to  diversion  and  applica- 
PUSH  BUTTONS  elsewhere 


Fig.  15  has  been  drawn  in  accordance  with 
this  principle  to  show  the  method  of  wiring  to 
be  followed  where  a  single  bell  is  to  be  worked 
by  either  one  of  two  separated  push  buttons.  It 
will  be  seen  that  in  case  either  of  the  buttons  is 
pressed  the  circuit  is  closed  and  the  mere  fact 
that  there  are  some  feet  of  wire  attached  that 
run  out  into  space,  will  have  no  effect  upon  the 
ringing  of  the  bell. 

Fig.  16  illustrates  a  case  of  the  wiring  of  an 
apartment  house  of  five  flats,  with  a  bell  in  each 
apartment  and  the  push  button  at  the  street 
door.  Here  each  one  of  the  five  push  buttons 


Electric  Bells  65 

controls  the  corresponding  bell,  and  none  other 
and  yet  all  of  the  buttons  and  all  of  th«  bells  are 


FIG.  16.— FIVE  BELL  CIRCUITS  LEADING  FROM 
A  SINGLE  BATTERY 

connected  to  the  battery  by  a  common  wire 
while  a  separate  and  distinct  one  runs  from  each 
button  to  its  own  particular  bell.  Take  No.  5 
as  an  example.  When  the  circuit  is  closed  at 
this  point,  the  current  flows  out  from  the  battery 
to  that  button  thence  to  bell  No.  5  and  back  to 
the  battery.  It  cannot  enter  and  operate  any  of 
+,he  other  four  bells  because  their  circuits  are 
open  at  their  respective  push  buttons. 

One  more  combination  will  be  shown  in  which 
a  single  battery  is  used  to  operate  two  bells 
worked  from  two  push  buttons,  the  bells  to  be 
located  at  the  opposite  button.  This  require- 
ment frequently  arises  where  it  is  desired  to 
transmit  signals  to  and  fro  between  separated 
points. 

In  this  case,  Fig.  17,  three  wires  are  used  to 


66  Electricity 

carry  two  complete  circuits,  for  if  the  button  A' 
is  pressed  the  bell  A  will  be  rung,  while  the  bell 
B'  is  rung  from  B. 


FIG.  17. — DOUBLE  BELL  AND  CALL  CIRCUIT 

This  principle  carried  out  into  a  greater  elabo- 
ration of  detail  will  serve  as  a  guide  for  the  anal- 
ysis of  much  that  is  apparently  intricate  in  the 
wiring  of  electric  bells  and  signals.  It  holds 
true  of  that  mass  of  wires  running  out  from  the 
large  enunciator  of  a  hotel  to  each  of  the  indi- 
vidual bedrooms  whereby  signals  and  calls  are 
transmitted  to  and  fro  without  requiring  the  use 
of  a  messenger.  The  one  prime  requisite  for  the 
proper  working  of  the  system  being  that  the 
wires  shall  be  thoroughly  insulated  from  each 
other  and  that  the  circuit  when  closed  shall  not 
be  diverted  to  other  points  than  that  at  which  it 
is  desired  that  it  shall  act. 

Like  all  other  pieces  of  mechanism  the  electric 
bell  requires  some  attention  and  is  subject  to 
some  ills.  The  care  that  should  be  bestowed 
upon  the  battery  has  already  been  mentioned  in 


Electric  JBells  67 

a  previous  chapter  and  need  not  be  recapitulated 
here.  Theoretically  there  should  never  be  any 
trouble  with  the  wires  after  they  have  once  been 
properly  located.  As  a  matter  of  practical  ex- 
perience they  will  frequently  get  out  of  order. 
Mice  and  rats  will  obtain  access  to  them  and 
gnaw  off  the  insulation  and  the  accidental 
dropping  of  a  nail,  or  the  accumulation  of  mois- 
ture may  serve  to  either  short  circuit  or  shut  off 
enough  of  the  current  to  prevent  the  ringing  of 
the  bell. 

Disuse  will  also  prevent  a  metallic  contact 
from  taking  place  between  the  moving  parts.  A 
little  rust  accumulating  on  the  metal  portions  of 
a  push  button  will  serve  to  hold  them  apart  and 
prevent  the  flow  of  the  current.  This  rust  is 
quite  apt  to  accumulate  where  the  button  simply 
drops  into  contact.  It  is  always  better  to  have 
two  such  surfaces  come  together  with  a  rubbing 
action,  as  this  tends  to  keep  them  bright  and  in- 
sures that  they  touch  metal  to  metal.  In  addi- 
tion to  these,  the  bells  are  liable  to  disarrange- 
ment through  the  loosening  of  the  screws  in  the 
binding  posts  and  the  shifting  of  the  adjustable 
stops  for  the  armature.  It  may,  therefore,  be 
necessary  to  make  quite  an  exhaustive  examina- 
tion of  the  whole  system  from  the  battery  to  the 


68  Electricity 

bell  before  a  trouble  can  be  located.  But  how- 
ever troublesome  this  may  be  and  however  much 
time  it  may  consume,  the  investigator  may  rest 
assured  that  there  is  never  anything  mysterious 
about  these  electrical  difficulties.  They  may  be 
troublesome  to  detect  but  when  found  they  will 
usually  be  seen  to  be  very  simple.  In  fact  it 
most  frequently  occurs  that  a  very  slight  defect, 
just  sufficient  to  prevent  the  proper  acting  of  the 
bell  or  signal,  is  far  more  difficult  to  detect  than 
one  of  greater  proportions,  just  as  a  gnat  crawl- 
ing on  the  ground  is  not  as  manifest  to  the  eye 
as  the  big  tumble  bug  of  a  beetle. 


CHAPTEE  Y 

THE    ELECTRIC    TELEGRAPH 

IT  is  quite  beyond  the  bounds  of  possibility  to 
estimate  the  benefit  that  has  accrued  to  mankind 
from  the  application  of  the  electric  current  to 
the  conveyance  of  messages  by  telegraphy.  As 
the  name  implies  it  is  the  writing  by  lightning, 
and  a  writing  by  lightning  both  in  the  means 
employed  and  the  speed  of  transmission.  Yet 
like  all  other  things  that  have  acquired  a  wide 
and  almost  universal  adoption  the  mechanism 
of  the  electric  telegraph  is,  in  itself,  exceedingly 
simple. 

The  motive  power  was,  for  many  years,  the 
battery  such  as  we  have  seen  employed  for  the 
ringing  of  bells  and  the  transmission  of  simple 
signals.  In  fact  it  is  in  itself  the  transmission  of 
the  simplest  of  signals. 

The  instrument  used  is  nothing  but  a  variation 
of  the  single  stroke  bell,  or  rather  it  would  be 
more  proper  to  say  that  the  single  stroke  bell  is 
a  mere  variation  of  the  ordinary  telegraph  in- 
strument or  sounder. 


70  Electricity 

Such  an  instrument  is  shown  in  Fig.  18,  and 
is  of  such  simplicity  in  detail  that  its  construc- 
tion will  be  readily  understood.  In  the  first 
place  it  should  be  mounted  upon  a  hardwood 
base,  A,  which  may  be  screwed  or  fastened  to  the 
operating  table.  To  this  is  attached  the  base  B 
of  the  instrument  itself,  which  should  be  of  brass 
and  drilled  with  holes  in  the  proper  places 


FIG.  18. — TELEGRAPH  SOUNDER 

through  which  small  countersunk  machine  screws 
are  inserted  to  hold  the  various  parts  in  their 
proper  positions. 

The  magnet  is,  of  course,  of  the  first  impor- 
tance. This  is  built  up  in  exactly  the  same  way 
as  that  used  and  already  described  in  connection 
with  electric  bells.  The  cores  need  not  be  more 


Cbe  Blcctrfc  ^Telegrapb  71 

than  one-half  inch  in  diameter  and  two  inches 
long,  but  the  amount  of  wire  should  be  varied 
according  to  the  distance  over  which  the  line  is 
to  be  worked.  "With  8  ozs.  of  No.  26  wire  a 
sounder  can  be  made  that  will  work  well  in  con- 
nection with  a  line  wire  fifteen  miles  long.  For 
short  circuits  the  amount  used  in  the  winding 
can  be  considerably  less.  Five  or  six  ounces  will 
be  quite  sufficient  for  short  circuits  or  where  the 
instrument  is  to  be  used  for  experimental  pur- 
poses only.  , 

The  armature  D  is  made  of  a  flat  bar  of  soft 
iron  from  A  inch  to  y&  inch  in  thickness  and  long 
enough  to  reach  out  to  the  outer  edges  of  the 
cores  of  the  magnet.  It  should  be  equal  to  the 
diameter  of  the  core  in  width.  This  may  be 
fastened  by  a  single  small  machine  screw  to  the 
armature  or  sounder  lever  E.  This  lever  is 
pivoted  on  points  at  the  end  of  the  screw  F 
which  passes  through  the  yoke  G  and  is  held 
from  turning  by  the  check-nut  H. 

All  parts  of  the  sounder  should  be  of  a  good 
quality  of  brass  with  the  exception  of  the  mag- 
net cores  and  armature  which  are  to  be  of  soft 
iron,  and  the  wiring  of  the  magnet  which  must 
be  of  well-insulated  copper  wire. 

If  restricted  only  by  the  main  portions  of  the 


72  Electricity 

instrument,  the  armature  lever,  which  vibrates 
on  two  screw  points  similar  to  F  entering  from 
either  side,  would  be  able  to  move  up  until  it 
struck  the  reversed  portion  of  the  frame  I  at  A, 
and  down  until  the  armature  lay  against  the 
cores  of  the  magnets.  To  prevent  this  range  of 
motion,  which  would  be  far  too  great,  two  ad- 
justing screws  K  and  L  are  used.  Their  con- 
struction is  very  clearly  shown  from  an  examina- 
tion of  the  engraving.  The  screw  L  passes 
through  the  lever  E  and  has  a  bearing  against 
the  main  portion  of  the  frame  I.  It  is  so  ad- 
justed that,  when  against  the  frame,  the  armature 
D  is  just  clear  of  the  cores  of  the  magnet.  The 
upward  motion  is  likewise  limited  by  the  screw 
K  to  what  may  be  required  under  the  varying 
conditions  of  battery  strength  to  produce  a 
sharp  clear  sound  to  indicate  the  motions  of  the 
armature. 

The  lever  E  has  a  downwardly  projecting  am 
against  which  a  spring  is  made  to  bear,  and 
whose  tension  is  regulated  by  means  of  an  ad 
justing  screw.  This  spring  tends  to  lift  the  lever 
and  hold  it  up  against  the  stop  K. 

The  wires  from  the  winding  of  the  magnets  are 
led  out  and  connected  to  two  binding  posts  M, 
only  one  of  which  can  be  seen  in  the  engraving; 


TTbe  Electric  Gelegtapb  73 

the  other  being  on  the  opposite  corner  and  con- 
cealed by  the  instrument  itself.  The  connection 
of  the  wires  is  made  at  the  bottom  beneath  the 
base  N.  These  binding  posts  have  a  small  hole 
B  near  the  top  in  which  the  wire  from  the  battery 
is  inserted.  This  wire  is  then  firmly  clamped  in 
position  by  the  screw  N. 

It  will  thus  be  seen  that  the  sounder  is  exceed- 
ingly simple  and  can  be  made  by  any  mechanic 
with  ordinary  tools  at  his  command. 

The  wiring  for  the  sounder  is  similar  in  every 
respect  to  that  used  for  the  electric  bell.  The 
difference  between  the  two  is  that,  in  the  case  of 
the  bell,  the  circuit  is  broken  when  it  is  not  in 
use,  whereas  in  the  case  of  the  telegraph  the 
circuit  is  kept  closed.  The  immediate  result  of 
this  is  that  the  battery  used  for  the  maintenance 
of  the  telegraph  circuit  is  exhausted  very  much 
more  rapidly  than  is  that  used  for  the  operation 
of  a  bell.  In  the  one  case  there  is  a  constant  flow  of 
current  and  in  the  other  an  intermittent  one,  that 
is  at  work  only  when  the  bell  is  actually  ringing. 

The  necessity  for  this  changed  condition  will 
be  readily  understood  when  the  requirements  of 
the  two  cases  are  considered.  With  the  bell  it 
is  usually  controlled  from  one  or  more  points 
always  acting  on  the  same  bell,  hence  the  closing 


74 


BlectrfcitB 


of  the  circuit  at  these  points  accomplishes  the 
purpose  of  doing  the  ringing.  In  the  case  of  the 
telegraph  it  is  necessary  to  operate  instruments 
from  two  widely  separated  points  over  one  and 
the  same  wire.  The  method  of  doing  this  work 
will  be  more  readily  understood  from  an  ex- 
amination of  the  engraving  Fig.  19,  in  which  the 
arrangement  of  a  telegraph  line  is  diagrammatic- 
ally  represented. 


FIG.  19.— TELEGRAPH  CIRCUIT 

The  battery  is  located  at  S  and  is  connected 
through  its  negative  pole  with  the  earth.  The 
wire  from  the  positive  pole  is  led  first  through 
the  coil  of  wire  of  the  first  instrument  at  I. 
This  instrument  is  usually  of  a  type  known  as  a 
relay  and  will  be  explained  later. 

From  the  relay  I  it  goes  to  the  first  operating 
key  C,  and  thence  on  through  the  successive  ke}7s 
C',  C"  and  relays  I'  and  I"  to  the  earth.  The 
keys  are  kept  closed  at  all  times  except  when  in 


Electric  tTelegrapb 


75 


use,  so  that  the  operator  at  each  station  can  con- 
trol the  working  of  the  line.  Thus,  suppose  the 
operator  at  I'  wishes  to  send  a  message  to  I",  he 
opens  his  key  and  by  making  and  breaking  the 
circuit,  is  able  to  cause  the  armatures  of  the  re- 
lays to  click  back  and  forth  between  their  stops. 
As  he  does  so  the  armatures  at  I,  V  and  I"  are 
operated  simultaneously  so  that  the  message  can 
be  read  at  any  station  along  the  line.  While  the 

clicking  of  an 
instrument  is  a 
notification  to 
the  operator  at 
any  point  that 
the  line  is  in  use. 

FIG.  20.— TELEGEAPH  OPERATING  KEY  ^  U 

for  the  working 

of  a  telegraph  circuit  is  shown  in  Fig.  20.  The  wire 
enters  and  is  attached  to  the  point  A,  which  is  insu- 
lated from  the  frame  and  other  portions  of  the  key. 
The  operating  lever  B  is  pivoted  between  two  screw 
points  and  to  it  is  attached  the  other  wire  lead- 
ing on  out  over  the  line.  The  lever  carries  a 
point  that  stands  opposite  to  A  and  which  may 
be  brought  into  contact  with  the  latter  by  press- 
ing down  upon  the  button-head  C.  When  the 
key  is  not  in  use  the  lever  D  is  pushed  beneath 


76  jeiectrfcttB 

the  contact-point  A,  as  shown  in  the  engraving, 
and  thus  establishes  an  electrical  contact  between 
it  and  the  frame  and  with  it  to  the  lever ;  thus 
closing  the  circuit.  When  the  key  is  to  be 
worked  the  lever  D  is  first  moved  out  to  break 
the  contact  at  A,  when  the  opening  and  closing  of 
the  circuit  is  controlled  by  the  working  of  the  lever. 
The  signals  of  the  electric  telegraph  are  con- 
veyed through  a  series  of  clicks  on  the  sounder 
instruments  known  as  dots  and  dashes,  because 
they  were  originally  inscribed  as  such  on  a  mov- 
ing strip  of  paper.  These  signals  are  made  in 
accordance  with  what  is  known  as  the  Morse 
code  and  are  ,  as  follows  for  the  several  letters 
of  the  alphabet: 

A. K  . U  .. 

B   ...          L  v  ...  — 

C  .  .     .  M W  . 

D  .  .  N    .  X  .  .  . 

E          .  O    .     .  Y    .  .     .  . 

F  .  .  P    Z    ..  .     . 

G .  Q..-.  &.... 

H  .  .  .  .  R    .     . .  ... 

I  ..  S    ...  ?    ..  • 

J  . .  T    ,    . .  

1  . .  5 9    .  .  

2  .  .  .  .  6  10 

3  ...  .  7 .. 

4  .     ,.  8  ... 


Gbe  Blectrfc  GeleQtapb  77 

These  letters  will  be  seen  to  vary  from  each 
other  in  some  cases  by  the  mere  intervals  and 
lapses  of  time  between  the  dots  and  dashes. 
Thus  H,  Y,  Z  and  &  are  formed  by  four  dots, 
spaced  and  sounded  at  different  intervals  apart. 

Originally  all  telegraphic  signals  were  regis- 
tered upon  a  moving  strip  of  paper  as  already 
stated.  The  method  is  shown  diagrammatically 
in  Fig.  21.  The  strip  of  paper  R  was  moved  at 
a  uniform  speed,  by 
clock-work  beneath 
the  roller  C,  while 
a  stylus  point,  at- 
tached to  the  arm- 

ature  of  the  instru-  FlQ    21>_TELEGRAPH  REGISTEE_ 
ment,  was  brought  ING  APPARATUS 

into  contact  with  it. 

This  method  has  now  been  abandoned  and  the 
reading  is  done  entirely  by  sound.  This  has 
added  very  materially  to  the  work  of  becoming 
a  telegraph  operator.  It  should  be  quite  pos- 
sible for  an  industrious  person  to  learn  to  send 
an  intelligible  message  in  from  five  to  six  days, 
whereas  it  might  take  as  many  months  to  learn 
to  receive  one  with  certainty  and  accuracy. 

This  reception  of  messages  by  ear  has  necessi- 
tated the  use  of  the  relay  instrument  already 


78  jeiectrtcfts 

referred  to.  The  current  passing  over  a  tele- 
graph line  is  usually  so  weak  that  the  click  of 
the  armatures  on  the  relay  instruments  on  the 
main  line,  is  so  indistinct  as  to  be  heard  with  diffi- 
culty. In  order  to  increase  the  noise  made  by 
the  instrument  a  sounder  operated  by  a  local 
battery  is  used.  The  strength  of  this  battery  is 
such  that  the  armature  of  the  sounder  is  brought 
against  its  stops  with  sufficient  force  to  give 

out  a  distinctly 
audible  sound. 
The  movement 

of  the  armature 
FIG.    22.— TELEGRAPH   RELAY  AND       »    ,u  , 

SOUNDER  °f    the    relay 

is,  therefore, 

merely  used  to  open  and  close  the  circuit  of  the 
local  battery  by  which  the  sounder  is  operated. 

The  method  of  wiring  for  the  relay  and  sounder 
is  shown  diagrammatically  in  Fig.  22. 

A  is  the  relay  instrument,  which  is  exactly 
like  the  sounder  except  that  it  is  so  constructed 
that  its  armature  can  be  made  to  close  and  open 
an  electric  circuit.  B  and  C  are  the  positive  and 
negative  wires  of  the  main  line  as  they  enter 
and  leave  the  coils  of  the  relay  magnet.  D  is 
the  armature  of  the  relay  and  is  made  to  con- 
nect electrically  with  one  pole  of  the  battery  F. 


Gbe  Electric  Gelesrapb  79 

The  sounder  coil  E  has  one  wire  leading  to 
the  stop  G  for  the  relay  armature,  and  the  other 
to  one  of  the  poles  of  the  battery  F.  From  the 
other  pole  of  the  battery  a  wire  is  led  to  the 
insulated  armature  of  the  relay.  It  is  evident, 
then,  that,  as  the  armature  D  moves  back  and 
forth  under  the  influence  of  its  magnet,  it  will 
make  and  break  the  circuit  of  the  sounder  and 
cause  the  armature  of  the  latter  to  move  to  and 
fro  between  its  stops  and  give  the  desired  signals 
to  the  receiving  operator. 

In  regard  to  the  amount  of  current  used  upon 
telegraph  lines,  it  is  very  weak  and  is  hardly 
perceptible  when  passed  through  the  body.  For 
the  main  line  it  amounts  to  from  forty  to  fifty 
thousandths  of  an  ampere,  or,  as  it  is  technically 
expressed,  to  from  forty  to  fifty  milliamperes. 
At  times  it  may  even  drop  to  fifteen  milliamperes 
and  still  give  good  and  satisfactory  service  in 
working. 

The  tension  or  voltage  of  the  current  is,  how- 
ever, quite  high.  Owing  to  the  distances  over 
which  the  ordinary  telegraph  line  is  operated, 
the  resistance  of  the  wires  is  very  great  and  the 
voltage  must  be  increased  in  almost  direct  pro- 
portion to  the  distance  in  order  to  overcome  this 
resistance.  For  this  reason  a  large  and  powerful 


so  ^Electricity 

battery  must  be  employed.  Xo  fixed  rule  can 
be  given  for  the  determination  of  the  strength 
of  current  to  be  used,  as  it  will  depend  upon 
local  conditions  such  as  climate,  the  character  of 
the  line,  number  and  kind  of  instruments  and 
the  like.  A  roughly  broad  statement  may  be 
made  to  the  effect  that  ordinarily  one  DanielFs 
cell  can  be  depended  upon  to  give  one  volt,  and 
that  the  voltage  should  be  equal  to  the  number 
of  miles  between  terminals. 

Thus  for  a  line  one  hundred  and  fifty  miles 
long  a  battery  of  one  hundred  and  fifty  cells  will 
be  required,  and  the  voltage  will  touch  the  same 
figure.  It  is  customary,  however,  to  duplicate 
this  battery  by  placing  one  of  the  strength  named 
at  each  end  of  the  line.  This  is  in  order  to  ob- 
tain a  margin  of  excess  to  insure  the  proper  work- 
ing of  the  line  under  all  of  the  adverse  conditions 
to  which  it  may  be  subjected. 

There  is  always  more  or  less  leakage  of  the 
current  from  a  line  of  any  length  owing  to  bad 
insulation  and  changing  weather  conditions.  A 
heavy  rainstorm  by  which  the  wires,  insulators 
and  poles  are  wet  will  cause  a  very  serious  leak- 
age of  the  current  as  a  result  of  the  deposited 
moisture,  since  water  is  of  itself  a  fairly  good 
conductor.  It  is,  therefore,  well  to  bear  in  mind 


Gbe  Electric  Gelearapb  81 

the  caution  given  in  connection  with  electric 
bells  to  always  provide  an  excess  of  current  over 
that  which  the  actual  requirements  of  the  case 
make  necessary.  This  applies  with  especial  force 
to  private  telegraph  lines. 

As  for  the  battery  required  to  operate  a 
sounder,  two  Daniell's  cells  are  all  that  will  be 
needed.  This  is  practically  the  standard  number 
that  is  used  in  all  stations. 

In  erecting  a  telegraph  line,  but  one  wire  is 
used,  the  return  current  being  carried  by  the 
ground  as  shown  in  Fig.  19.  It  is  necessary  in 
establishing  the  ground,  as  it  is  called,  that  the 
wires  should  be  carried  down  below  the  point  of 
permanent  moisture  and  that  they  should  be  put 
in  close  and  intimate  electrical  contact  with  the 
soil. 

It  will  not  do,  then,  to  merely  push  the  wire 
down  into  the  ground.  It  should  be  brazed  to  a 
copper  plate  and  the  latter  should  be  buried 
below  the  water  or  moisture  line  and  the  earth 
firmly  packed  about  it.  The  wires  may  also  be 
fastened  to  gas  or  water  pipes  or  the  plate  may 
be  buried  near  a  stream  of  water  or  even  lowered 
into  a  well. 

If  the  wires  are  to  be  attached  to  water  or  gas 
pipes  the  latter  should  be  filed  clean  and  bright 


82  ^electricity 

before  the  connection  is  made.  Even  then  they 
may  prove  to  be  an  unsatisfactory  ground  be- 
cause of  some  insulating  or  highly  resisting  ma- 
terial having  been  used  to  form  their  own  joints. 

It  may  be  taken  as  an  axiom  that  many  if  not 
most  of  the  troubles  experienced  with  private 
telegraph  lines  arise  from  an  improper  or  insuffi- 
cient grounding  of  the  wires. 

For  short  lines  it  will  usually  be  found  to  be 
inadvisable  to  attempt  to  use  the  earth  for  the 
return  circuit.  The  added  expense  of  putting  in 
an  extra  wire  to  complete  the  circuit  will  be 
amply  repaid  by  the  convenience  and  freedom 
from  annoyance  due  to  the  failure  of  the  current, 
that  would  otherwise  occur  and  the  facility  with 
which  all  parts  of  the  circuit  can  be  inspected 
and  repaired. 

From  what  has  been  said  it  will  be  seen  that 
the  operation  of  long  circuits  involves  the  use  of 
very  large  and  proportionately  heavy  batteries. 
As  the  cell  of  a  Daniell's  battery  for  such  a  serv- 
ice should  be  in  a  glass  jar  at  least  five  inches  in 
diameter  by  six  inches  deep,  the  weight  and  bulk 
of  batteries,  numbering  cells  by  the  hundreds,  is 
a  matter  of  serious  importance,  which  is  not  less- 
ened by  the  trouble  and  expense  of  maintenance. 

This  difficulty  has  been  obviated  by  the  appli- 


Gbe  Electric  Gelegrapb  83 

cation  of  the  dynamo  to  the  generation  of  the- 
current  used  for  telegraphic  purposes.  The 
method  ordinarily  employed  is  to  connect  several 
dynamos  in  series  exactly  as  the  batteries  have 
already  been  described  as  being  connected,  and 
increasing  the  voltage  from  one  to  the  other  by 
this  means.  The  voltage  used  on  long  circuits  is 
somewhat  less  per  mile  than  that  previously  given 
in  the  rough  statement  of  what  should  be  pro- 
vided for.  It  has  been  found  that  two  hundred 
and  forty  volts  is  sufficient  for  a  circuit  of  four 
hundred  miles. 

As  far  as  the  operators  and  the  working  of  the 
line  are  concerned  there  is  no  difference  between 
the  using  of  a  current  generated  by  batteries  or 
dynamos.  The  advantages  possessed  by  the  lat- 
ter are  greater  compactness,  decreased  cost  of 
installation  and  maintenance  and  increased  re- 
liability. 

There  are  some  precautions  that  should  be 
taken  in  the  installation  of  any  telegraph  line,  no 
matter  how  short,  where  the  wires  are  stretched 
out  of  doors  and  are  exposed  to  the  elements. 

One  of  these  precautions  is  the  protection  of 
the  instruments  from  injury  by  lightning. 
Wherever  a  bare  wire  is  out  of  doors  it  is  sub- 
jected to  the  influence  of  the  electrical  condition 


84 

of  the  atmosphere.  As  it  is  usually  a  far  better 
conductor  than  the  other  objects  with  which  it  is 
surrounded  and  as  it  is  usually  led  to  a  direct 
connection  with  the  ground,  it  becomes  a  light- 
ning rod  of  great  extent  ready  to  receive  and 
convey  any  discharge  that  may  be  delivered  to  it. 

It  has  already  been  pointed  out  that  the  con- 
veyance of  an  electrical  current  through  any 
wire  whatsoever  is  always  accompanied  by  the 
development  of  more  or  less  heat.  The  stronger 
the  current  and  the  greater  the  resistance  of  the 
wire  the  higher  will  be  the  temperature  devel- 
oped in  the  wire. 

As  the  wire  used  in  the  coils  of  a  telegraph  in- 
strument is  smaller  than  that  used  out  upon  the 
line,  its  resistance  is  greater  and  the  amount  of 
heat  developed  in  it  with  the  passage  of  a  given 
amount  of  current  will  also  be  greater.  It  fol- 
lows, then,  that  a  current,  which  might  have  no 
appreciable  effect  upon  a  line  wire  might  heat  to 
redness  and  destroy  the  wiring  of  an  instrument. 

To  prevent  such  an  accident  from  occurring  as 
the  result  of  a  lightning  discharge,  lightning 
arresters  should  be  placed  in  the  circuit.  The 
simplest  form  which  this  can  take  is  that  of 
a  fine  piece  of  wire  of  high  resistance.  As  soon, 
therefore,  as  the  intensity  of  the  current  rises 


Gbe  Blectric  Getegrapb  85 

above  that  which  it  is  desired  that  the  wires 
shall  carry,  this  small  wire  is  melted  and  is 
broken,  thus  opening  the  circuit  and  preventing 
the  excess  current,  with  which  the  line  is  charged, 
from  passing  through  the  instruments  and  injur- 
ing them.  This  is  the  easiest  method  for  pri- 
vate lines  that  are  to  be  erected  and  operated  by 
the  owner. 

For  regular  telegraphic  service  more  elaborate 
provisions  are  made  with  regularly  constructed 
lightning  arresters.  Some  of  these  are  arranged 
to  automatically  cut  out  with  a  spring  as  soon  as 
the  voltage  exceeds  a  certain  predetermined 
figure.  Others  are  provided  with  a  plug  which 
may  be  withdrawn  whenever  the  dancing  of  the 
armature  of  the  instrument  shows  that  the  line 
is  subjected  to  outside  electrical  influences  at 
some  point  along  it. 

It  is  always  well  to  provide  even  short  private 
lines  with  one  of  these  plugs  so  that  the  instru- 
ments may  be  entirely  disconnected,  whenever  it 
is  known  that  the  line  is  not  to  be  used  for  any 
length  of  time.  This  makes  it  possible  to  dis- 
connect at  night  during  the  season  of  electrical 
storms.  There  are  several  ways  in  which  this 
plug  can  be  made,  the  simplest  being  that  of 
placing  two  binding  posts  like  Fig.  23,  in  the 


86 


circuit  and  connecting  these  with  a  strong  cop- 
per wire,  which  may  be  easily  removed  by  the 
slackening  of  one  of  the  set-screws. 

This  plug  should  not  be  used  to  the 
exclusion  of  the  fusible  wire,  but 
merely  as  a  protection  to  the  latter  and 
to  avoid  the  annoyance  of  replacing  the 
same  when  the  danger  of  its  destruc- 
tion begins  to  manifest  itself. 

No  attempt  has  been  made  in  this 
chapter  to  deal  with  the  intricacies  of 
duplex  and  quadruplex  telegraphy,  by 
means  of  which  two  messages  may  be 
sent  in  opposite  directions  over  one  wire  at  the 
same  time,  but  merely  to  handle  the  matter  in  its 
simplest  form,  and  in  a  way  to  guide  those  who 
wish  to  use  it  on  a  small  scale. 


CHAPTEE  VI 

THE  TELEPHONE 

THE  telephone  strictly  speaking  is  au  instrtu 
ment  with  which  sounds  can  be  conveyed  from 
one  point  to  another  by  means  of  the  electric 
current.  There  are,  however,  other  instruments, 
improperly  called  telephones,  by  which  the  same 
object  may  be  attained  and  in  which  no  electrical 
current  is  used  at  all. 

As  these  so-called  mechanical  telephones  are 
very  frequently  made  and  installed  for  private 
use  it  may  be  well  to  give  a  brief  description  of 
their  construction  and  principle  of  operation. 

Sound  is  a  form  of  wave  motion  which  may  be 
imparted  to  solids,  liquids  or  gases,  and  which, 
when  impinging  on  the  drum  of  the  ear,  pro- 
duces the  sensation  which  we  know  by  that 
name.  That  the  sound  waves  can  be  carried 
through  solids  and  liquids  as  well  as  gases  is  evi- 
denced by  the  loud  apparent  noise  made  by  the 
striking  of  stones  together  when  the  head  of  the 
listener  is  below  water.  The  same  phenomena  is 

87 


88  Electricity 

manifested  by  the  conveyance  of  sound  waves 
along  pipes  that  are  struck  with  a  hammer. 

The  principle,  then,  upon  which  a  mechanical 
telephone  may  be  made  to  operate  is  that  of  the 
conveyance  of  a  sound  through  the  metal  of  a 
wire.  Means  must  be  supplied  of  imparting  the 
sound  vibrations  to  one  end  of  the  wire  and  of 
receiving  them  from  the  same  at  the  other. 
Owing  to  the  resistance  of  the  metal  to  the  pas- 
sage of  these  wave  motions,  the  distance  over 
which  they  can  be  carried  is  limited.  As  a  mat- 
ter of  fact  it  is  somewhat  difficult  to  get  a  me- 
chanical telephone  to  work  when  the  distance  is 
more  than  a  mile  between  terminals. 

The  construction  of  a  mechanical  telephone  for 
household  or  office  purposes  is  very  simple.  The 
most  satisfactory  working  can  be  obtained  by 
using  a  drumhead  or  piece  of  parchment 
stretched  over  a  frame  and  held  firmly  in  the 
position  it  is  to  occupy.  A  piece  of  steel  wire  is 
let  through  the  centre  of  the  drumhead  and 
fastened  to  a  small  button,  which  may  thus  be 
held  firmly  against  the  head.  The  wire  is  car- 
ried to  another  similar  drumhead  and  similarly 
fastened.  It  should  be  carried  as  direct  as  pos- 
sible with  the  minimum  number  of  bends  and 
none  of  them  short  ones. 


Gbe  Gelepbone  89 

A  person  standing  in  front  of  such  a  drum- 
head and  speaking,  can  be  heard  at  the  other. 
Attention  may  be  called  by  tapping  on  one  head 
with  the  finger.  The  transference  of  conversa- 
tion over  the  line  can  be  prevented  by  merely 
hanging  a  curtain  loosely  before  the  receiving 
drumhead.  The  diaphragms  or  drumheads  may 
be  replaced  if  desired  by  a  piece  of  ferrotype, 
such  as  the  so-called  tintype  pictures  are  made  upon. 

The  true  telephone,  on  the  other  hand  de- 
pends upon  an  electric  current  "for  the  transfer- 
ence of  the  sound  waves  from  one  point  to  an- 
other, and  the  connecting  wire  is  not,  in  any 
way  subjected  to  their  vibrations. 

Before  taking  up  the  construction  of  the  tele- 
phone, a  few  words  regarding  magnetism  and  its 
influences  will  be  needed.  In  the  first  chapter  it 
was  explained  that  a  magnet  has  the  power  to 
attract  to  itself  small  iron  filings  with  which  it 
may  be  brought  into  contact.  If  a  magnet  be 
placed  beneath  a  sheet  of  paper  and  iron  filings 
be  first  scattered  over  the  top  and  the  paper  then 
slightly  jarred,  they  will  arrange  themselves 
along  certain  lines  of  force  as  shown  in  Fig.  24. 
They  will  cluster  most  densely  about  the  poles 
of  the  magnet  and  lead  out  and  back  in  diverg- 
ing lines  from  one  pole  to  the  other. 


90 


jeiectrfcftB 


It  has  been  shown  that,  if  an  electric  current 
be  made  to  pass  in  a  coil  around  a  bar  of  iron, 

the  latter  will  become 
magnetized.        The 
converse    of    this  is 
equally  true,  that  if 
a  magnet  be  moved 
through     a    coil    of 
FIG.  24.— MAGNETIC  FIELD       wire,  an  electric  cur- 
rent    will    be    gen- 
erated and  made  to  pass  through  the  wire  pro- 
vided the  ends  are  brought  together  so  as  to  form 
a  closed  circuit. 

These  simple  phenomena  lie  at  the  base  of  the 
operation  of  the  electric  telephone  as  well  as  that 


FIG.  25.  SECTION  OF  BELL  TELEPHONE  RE- 
CEIVER 

of  all  dynamos  and  motors  and  will  be  more 
fully  explained  later. 

Fig.  25  is  a  sectional  engraving  of  the  double- 
pole  Bell  telephone  receiver. 


Gbe  ftelepbone  91 

The  working  parts  consist  of  a  horseshoe  mag- 
net A,  two  soft  iron  cores  wound  as  magnets  B 
and  C  and  a  diaphragm  D. 

The  horseshoe  magnet  is  permanent  and  car- 
ries the  soft  iron  cores  which  are  in  metallic  con- 
tact with  it  and  which  thus  form  short  polar  ex- 
tensions. The  wires  are  led  out  from  the  wind- 
ings to  the  binding  posts  at  the  farther  end  to 
which  the  wires  to  complete  the  circuit  to  the 
other  instrument  are  fastened. 

The  operation  of  the  instrument  is  as  simple 
as  its  .construction.  A  noise,  such  as  speaking, 
made  in  front  of  the  diaphragm,  causes  the  latter 
to  vibrate  just  as  in  the  case  of  the  mechanical 
telephone.  This  vibration  causes  a  variation  in 
the  number  and  intensity  of  the  magnetic  lines 
of  force  cutting  the  coils  around  the  soft  iron 
cores.  This  variation  of  intensity  and  number 
has  the  same  effect  as  a  moving  of  the  core 
through  the  coils,  as  may  be  inferred  from  an 
examination  of  Fig.  24.  The  result  of  this  is 
that  an  electric  current  is  generated  and  caused 
to  pass  through  the  coil  of  wire  about  the  cores. 

If  now  these  wires  are  carried  out  and  con- 
nected to  another  similar  receiver  so  that  the 
wire  from  B  leads  to  the  coil  corresponding  to  C, 
and  vice  versa,  the  current  generated  at  the  first 


92  jeiectricfts 

diaphragm  will  cause  a  variation  of  the  intensity 
of  the  magnetism  in  the  cores  in  front  of  the 
second  diaphragm. 

In  explanation  of  this  statement  the  reader 
will  remember  that  the  intensity  of  the  electric 
current  passing  through  a  coil  controls  the 
strength  of  the  magnet.  So,  in  this  case,  the 
strength  of  the  cores  is  varied  by  the  variation 
of  the  current  produced  by  the  vibration  of 
the  first  diaphragm.  This  causes  corresponding 
change  to  take  place  in  the  attraction  of  the 
cores  for  the  diaphragm;  in  harmony  with  the 
vibrations  of  the  transmitting  diaphragm,  causing 
•it  to  emit  similar  though  somewhat  weaker 
sounds. 

From  this  it  appears  that  an  instrument  like 
that  shown  in  Fig.  25  may  be  used  both  as  a 
transmitter  and  receiver.  The  former  is  the 
term  applied  to  the  instrument  at  which  the 
message  is  started,  and  the  latter  to  that  at  which 
it  is  received. 

In  the  construction  of  the  instrument  the 
screw  E,  at  one  end,  is  a  holding  and  adjusting 
screw  only.  It  holds  the  permanent  horseshoe 
magnet  in  position  and  serves  to  adjust  it  so  that 
the  ends  of  the  cores  will  be  at  the  proper  dis- 
tance from  the  diaphragm  in  order  to  produce 


Gbe  Gelepbone  93 

the  best  results.  The  diaphragm  itself  is  held 
by  a  cap  screwed  down  over  it  and  clamping  it 
around  the  edge. 

In  practice  it  has  been  found  to  be  preferable 
to  use  separate  instruments  for  the  transmitting 
and  reception  of  telephone  messages. 

The  transmitter  that  has  received  the  widest 
application  is  the  one  known  as  the  Blake,  prob- 
ably because  it  was  the  first  satisfactory  one  pro- 
duced. It  is  dependent  for  its  action  upon  the 
fact  that,  if  an  electric  current  is  made  to  pass 
through  two  non-oxidizable  substances  in  loose 
contact  with  each  other,  and  these  are  put  into 
vibration,  the  resistance  offered  to  the  passage  of 
that  current  is  subject  to  wide  variations.  This 
is  due  to  the  increase  and  decrease  in  intimacy 
of  contact,  by  which  the  resistance  is  correspond- 
ingly increased  or  diminished. 

Thus,  in  the  Blake  transmitter,  the  current  is 
made  to  pass  through  a  piece  of  hard  carbon  that 
is  in  loose  contact  with  a  piece  of  platinum. 

The  construction  of  this  transmitter  is  shown 
in  section  in  Fig.  26.  The  diaphragm  A  is  carried 
by  an  insulating  ring  clamping  and  holding  it  at 
its  edge.  Against  the  centre  of  this  diaphragm 
there  is  brought  to  bear  a  platinum  point  B. 
This  latter  is  held  by  a  thin  spring  C  which  is 


94 


Blectricfts 


held  by  a  piece  of  insulation  to  the  upper  arm  of 
the  heavy  lever  D.  This  latter  is  itself  carried 
by  the  spring  E  and  adjusted  to  position  by  the 
screw  F.  Dropping  down  from 
the  upper  end  of  the  lever  is  a 
spring  G  to  the  lower  end  of 
which  the  carbon  button  H  al- 
ready referred  to  is  attached. 
This  is  in  contact  with  the 
platinum  point. 

The   wiring  from  the   electric 
circuit  enters  through  the  insula- 
tion at  the  top  of  the  lever  D 
and  is  led  out  from  the  bottom 
of  the  same.     The  course  of  the 
FIG.  26.— SECTION  current  through  the  transmitter  is 
OF  BLAKE  TELE-  first   over   the   spring   C    to   the 
PHONE    TRANS-  platinum  point  B,  to  the  carbon 
button  H,  to  the  spring  G,  to  the 
lever  D  and  out  at  the  bottom  of  the  bracket  as 
shown. 

The  action  of  the  transmitter  is  as  follows  : 
The  speaker  in  front  of  the  diaphragm  causes 
it  to  vibrate  in  unison  with  the  pitch  of  the 
utterance.  This  vibration  is  communicated  to 
the  platinum  point  and  by  it  to  the  hard  carbon 
button.  The  tension  of  the  spring  by  which  the 


Gbe  Gelepbone  95 

latter  is  supported  is  varied  by  this  vibration  caus- 
ing a  variation  in  the  pressure  of  contact  be- 
tween the  two  parts  thus  producing  a  correspond- 
ing variation  in  the  resistance  to  the  current 
already  indicated. 

It  will  be  noticed  that  in  this  transmitter  the 
horseshoe  magnet  and  soft  iron  cores  are  missing 
and  that  the  generation  of  an  electric  current  by 
the  variation  of  the  lines  of  force  of  a  magnet 
does  not  take  place. 

This  transmitter 
is  known  as    the 


microphone  trans- 

mitter    and    is    a     Fl0'  27--SllfGLE  TELEPHONE  Cte- 

CUIT 

modification  of  the 

Hughes  microphone,  whose  action  is  dependent 
upon  the  principle  already  explained  regarding 
the  variation  of  the  resistance  to  an  electric  cur- 
rent by  the  vibration  of  two  loose  pieces  in  contact. 
This  instrument,  then,  depends  upon  some  out- 
side source  of  electricity  for  the  operating  cur- 
rent and  merely  changes  the  amount  of  flow  of 
this  current  to  produce  the  desired  effect  upon 
the  receiver.  This  current  may  be  furnished  by 
an  ordinary  Daniell's  or  Leclanche  battery  and 
the  wiring  for  a  simple  circuit  would  be  done  as 
shown  in  Figs.  26  and  27. 


96 


Blectrfcfts 


In  this  the  current  starts  from  the  battery  and 
flows  out  over  the  wire  to  the  transmitter,  thence 
to  the  coils  of  the  receiver  and  on  back  to  the 
battery. 

With  such  a  combination  as  that  given  in  this 
illustration,  the  transmission  of  sound  would  be 
in  one  direction  only,  namely  from  the  trans- 
mitter to  the  receiver.  Though  the  action  of  the 
receiver  might  send  back  some  sound  it  could  not 
be  made  available. 

In  order,  then, 
that     the    tele- 
phone     circuit 
may  be  used  to 
transmit   sound 
FIG.  28.— SIMPLE  TELEPHONE  CIRCUIT     in    both    direc- 
WITH  RECEIVER  AXD  TRANSMITTER       tions    and    thus 

be  employed  for  conversational  purposes,  there 
should  be  a  receiver  and  transmitter  at  each  end 
of  the  line. 

The  wiring  for  such  a  combination  is  very  sim- 
ple and  consists  in  putting  the  extra  transmitter 
and  receiver  into  the  circuit  as  shown  in  Fig.  28. 
Here  two  batteries  are  used  just  as  in  a  telegraph 
circuit  for  the  sake  of  having  an  ample  current 
available  and  not  because  a  battery  at  one  end  of 
the  line  could  not  be  made  to  do  the  work.  The 


ttbe  Gelepbone  97 

'line  is  also  shown  with  a  return  wire,  which,  as 
in  the  case  of  the  telegraph  should  always  be 
used  on  short  lines,  owing  to  the  difficulty  of 
securing  a  satisfactory  ground  return. 

As  the  distance  between  the  transmitter  and 
receiver  of  a  telephone  circuit  increases,  the 
greater  is  the  resistance  offered  by  the  line 
wires,  the  greater  the  current  required  to  operate 
it  and  the  less  the  influence  of  the  transmitter  in 
causing  a  variation  of  the  intensity  of  that  cur- 
rent. After  a  time  the  distance  would  become 
so  great  that  the  proportional  variation  of  resist- 
ance set  up  at  the  transmitter  as  compared  with 
the  total  resistance  of  the  line  would  be  so  slight 
as  to  be  inappreciable.  When  this  point  was 
reached  there  would  be  no  perceptible  effect  at 
the  receiver  and  no  sound  would  be  heard  at  that 
point. 

In  order  to  obviate  this  difficulty  recourse  is 
had  to  the  induction  coil. 

Just  as  we  have  seen  the  magnet  to  be  sur- 
rounded by  lines  of  force  that  will  cause  iron 
filings  to  arrange  themselves  in  certain  definite 
positions  on  a  sheet  of  paper ;  so  a  wire,  through 
which  a  current  of  electricity  is  passing,  is  sur- 
rounded by  corresponding  lines  of  force  that 
have  a  direct  influence  on  other  wires  in  their 


98  ^electricity 

own  neighborhood.  This  influence  causes  an  in- 
duced electrical  current  in  the  second  wire.  Thus, 
if  two  wires  are  laid  side  by  side  and  an  electric 
current  be  made  to  pass,  from  the  positive  pole 
of  a  battery,  over  one  of  the  wires  from  right  to 
left,  an  induced  current  will  appear  in  the  second 
wire  flowing  from  left  to  right. 

In  like  manner  if  the  wire  carrying  the  primary 
current,  or  the  one  generated  by  the  battery,  is 
wound  about  a  soft  iron  core,  the  latter  will  be- 
come magnetized  to  a  degree  dependent  upon 
the  number  of  ampere  turns.  A  second  coil, 
carried  around  this  same  core,  will  have  an  in- 
duced or  secondary  current  passing  through  it. 

Advantage  is  taken  of  these  facts  to  cause  the 
transmitter  to  so  influence  the  current  of  the 
main  line  that  the  proper  effect  is  produced  at 
the  receiver.  The  practical  working  of  this  ar- 
rangement is  that  the  primary  current,  or  the 
one  generated  direct  by  the  battery  is  compara- 
tively large  and  the  undulations  are  not  of  great 
magnitude.  In  the  secondary  current,  on  the 
other  hand,  owing  to  the  greater  number  of 
windings  in  the  coil,  the  intensity  is  higher  and 
the  fluctuations  correspondingly  greater. 

The  modification  that  should  be  made  in  the 
connections  shown  in  Fig.  28,  consist  in  the  in- 


Gbe  ftelepbone  99 

troduction  of  the  induction  coil  into  the  circuits 
of  the  two  local  batteries.  The  method  by  which 
this  is  accomplished  is  clearly  shown  in  Fig.  29. 

As  far  as  the  local  battery  is  concerned  it  will 
be  seen  that  its  circuit  is  confined  strictly  to  its 
own  transmitter.  Thus,  take  the  connections  at 
the  station  A .  The  current  flows  from  the  battery 
B  to  the  transmitter  and  thence  through  the  in- 
duction coil  D  and  back  to  the  battery.  At  the 


FIG.  29.— TELEPHONE  CIRCUIT  WITH  IN- 
DUCTION COILS 

station  C  there  is  a  similar  connection  for  the 
transmitter.  There  is  no  direct  connection  of 
the  primary  current  with  the  receiver  either  at 
its  own  or  the  opposite  end  of  the  telephone  cir- 
cuit. This  connection  is  made  by  means  of  the 
induced  current. 

Starting  from  the  induction  coil  at  D  the  cur- 
rent goes  out  over  the  line  wire  to  the  induction 
coil  of  the  station  C,  thence  to  the  receiver  of 


ioo  Blectrfcfts 

that  station,  back  to  the  receiver  of  station  A  and 
finally  completes  the  circuit  by  entering  the  in- 
duction coil  D. 

This  is  the  simple  arrangement  in  accordance 
with  which  the  speaking  telephone  is  constructed 
and  worked.  There  are  some  complications  and 
delicacies  of  adjustment  that  might  make  it  diffi- 
cult for  the  amateur  to  meet  were  he  to  attempt 
to  make  one  for  his  own  use,  but  there  is  nothing 
intricate  in  the  erection  and  maintenance  of  the 
same  when  the  operating  parts  have  once  been 
obtained. 

The  instrument  as  thus  described  is  by  no 
means  a  complete  and  perfect  telephone,  for  even 
ordinary  use.  In  addition  to  the  apparatus  that 
is  merely  capable  of  transmitting  spoken  words 
from  one  point  to  another,  there  must  be  some 
means  of  attracting  the  attention  of  the  parties 
located  at  one  instrument  when  those  at  the 
other  wish  to  speak  to  them. 

The  ordinary  method  of  doing  this  is  by  the 
use  of  a  call  bell.  This  may  be  independent  of 
the  telephone  but  using  the  same  line  wire  and 
may  take  the  form  of  the  ordinary  bell  described 
in  a  preceding  chapter.  Such  an  arrangement  is, 
however,  seldom  used,  but  in  its  stead  the  mag- 
neto switch  bell  or  a  battery  bell  is  used. 


Ebe  Gelepbone  101 

In  the  former  a  small  dynamo  is  placed  within 
the  telephone  case,  and  is  t/u-rh^d  by  a  .handle 
upon  the  outside.  The  principles  underlying  the 
construction  of  the  dynamo*  wilj  be  f.uHy  a^piaiiied 
in  the  chapter  on  Dynamos  and  Motors. 

Suffice  it,  for  the  present,  to  say  that  the  cur- 
rent generated  by  this  small  dynamo  is  led  out 
over  the  line  wire  to  the  further  end  where  it  is 
made  to  ring  the  call  bell.  The  introduction  of 
this  magneto  bell  adds  a  little  more  to  the  com- 
plication in  that  it  is  desirable  that  the  trans- 
mitter and  receiver  should  be  out  of  the  circuit 
when  the  instrument  is  not  in  use,  and  that  the 
bell  should  be  in  circuit.  This  is  accomplished 
by  the  weight  of  the  receiver  pulling  down  the 
lever  upon  which  it  is  carried,  when  not  in  use 
and  cutting  out  the  transmitter  and  receiver  and 
putting  the  bell  in  circuit.  The  removal  of  the 
receiver  from  the  hook  allows  a  spring  to  lift  the 
lever,  a  movement  which  cuts  out  the  bell  and 
puts  the  transmitter  and  receiver  into  the  circuit. 

The  battery  switch  bell  is  in  itself  constructed 
like  the  vibrating  bell  already  described.  The 
ringing  is  accomplished  by  the  pressing  of  a 
push  button  on  the  side  of  the  case  while  the  re- 
ceiver is  still  hanging  upon  its  hook  at  the  side. 
On  removal  of  the  receiver  a  spring  lifts  the 


102  Blectrfcftg 

lever  and,  as  in  the  previous  instance,  throws  the 
bell  out  -of  and  the -receiver  and  transmitter  into 
circuit. 

These  are  tb.3  principles  irpon  which  the  whole 
telephonic  circuit  are  worked  and,  like  all  other 
electrical  instruments,  they  are  exceedingly 
simple  in  theory. 

Owing,  however,  to  the  contracted  limits  of  a 
telephone  case  into  which  it  is  desired  to  stow  a 
considerable  mass  of  wiring  and  apparatus,  the 
whole  scheme  will  appear  upon  first  examination, 
to  be  a  complicated  and  chaotic  tangle.  But  this 
is  far  from  being  the  case,  and  the  recommenda- 
tion of  dissection  is  made  to  the  student  of  the 
telephone,  just  as  it  is  made  to  the  student  of 
human  anatomy. 

It  is  quite  necessary  that  a  word  of  caution 
should  be  added,  in  the  closing  of  this  chapter, 
regarding  the  stringing  of  telephone  wires.  In 
the  ordinary  electrical  circuit  where  some  visible 
work  is  to  be  done  like  the  ringing  of  a  bell  or 
the  moving  of  an  armature  or  a  telegraph  instru- 
ment the  current  must  be  of  considerable  in- 
tensity and  variations  in  that  intensity  are  un- 
noticed, provided  only  that  it  is,  in  itself,  strong 
enough  to  do  the  work  desired.  In  the  telephone 
circuit,  on  the  other  hand,  the  current  is  very 


Gbe  Gelepbone  103 

feeble  and  is  dependent  for  its  efficiency  upon 
these  same  variations  that  are  of  no  moment  in 
other  classes  of  work. 

We  have  seen  how  a  current  can  be  induced  by 
placing  one  wire  near  another  that  is  already 
carrying  a  current  from  a  primary  battery.  It 
follows,  then,  that  the  same  law  must  hold  good 
at  all  points  of  the  line,  and  the  proximity  of 
telegraph  or  electric  lighting  wires  to  a  telephone 
wire  may  set  up  induced  currents  in  the  latter, 
that  may  have  such  an  overpowering  effect  as 
not  only  to  prevent  the  transmission  of  speech 
from  one  end  of  the  line  to  the  other,  but  to 
cause  the  receivers  to  ring  with  noises  emanating 
from  remote  sources.  Indeed  it  was  these  in- 
duced currents  that,  in  the  early  days  of  tele- 
phony, caused  the  most  serious  trouble  to  the 
companies  and  their  patrons. 

The  telephone  wire  seems  to  be  particularly 
sensitive  to  the  influences  of  induction,  and  dis- 
tances of  several  feet,  that  would  ordinarily  be 
considered  quite  sufficient  to  protect  a  wire  are 
totally  inadequate  in  telephone  work. 

It  may  be  laid  down  as  a  fixed  basis  of  opera- 
tion that  telephone  wires  should  not  be  placed 
parallel  to  those  carrying  stronger  currents.  If 
approximate  parallelism  is  not  to  be  avoided,  the 


104  Electricity 

outgoing  and  return  wires  should  zigzag  on  their 
poles  so  that  first  one  and  then  the  other  shall  be 
the  nearer  to  the  wire  with  the  stronger  current. 
This  minimizes  the  effects  of  the  induction  by  ex- 
citing currents  in  opposite  directions  in  the  same 
circuit ;  currents  which  thus  serve  to  neutralize 
and  counteract  each  other. 

Where  telegraph  or  electric  lighting  wires  are 
to  be  crossed  by  a  telephone  circuit,  it  should  al- 
ways be  done  at  right  angles.  Such  a  crossing 
obviates  the  trouble  of  induction  entirely. 

As  for  the  return  wire  in  a  telephone  circuit 
the  rule  given  for  telegraph  wires  can  be  used 
and  for  the  same  reasons :  where  the  distances 
are  short  and  especially  where  they  are  limited 
to  the  confines  of  a  single  building,  use  a  wire 
for  a  return  circuit.  This  applies  also  to  the 
confines  of  a  factory.  For  greater  distances  the 
earth  may  be  used  for  the  return. 

The  most  satisfactory  wire  for  private  line 
work  will  be  found  to  be  No.  16,  made  of  hard 
drawn  copper  or  phosphor  bronze.  It  should  be 
well  insulated  and  drawn  taut.  For  inside  work 
it  should  be  covered,  but  may  be  bare  out-of- 
doors. 

After  the  instruments  have  been  set  up  they 
should  be  carefully  tested  to  see  that  the  ad- 


Gbe  Gelepbone  105 

justment  is  all  right.  The  first  thing  to  do  is  to 
take  down  a  receiver  and,  holding  it  to  the  ear, 
breathe  into  the  transmitter.  A  distinct  sound 
should  be  heard.  If  this  can  be  done,  an  as- 
sistant can  be  sent  to  the  other  end  to  ring  up 
and,  if  a  conversation  can  be  carried  on,  the  in- 
struments are  all  right. 

In  case  the  second  instrument  fails  it  should 
be  examined  and  adjusted  until  the  breathing 
test  gives  an  audible  sound. 

The  location  of  faults  and  failures  of  the  tele- 
phone is  sometimes  a  tedious  piece  of  work,  and 
can  only  be  touched  upon  here.  But  trouble  may 
occur  in  the  springs  by  which  the  pressure  be- 
tween the  platinum  point  and  the  carbon  is  regu- 
lated. In  the  receiver,  it  may  arise  from  the 
accumulation  of  dust  that  dampens  the  action  of 
the  diaphragm.  It  is  only  by  a  careful  exami- 
nation of  the  whole  apparatus  that  the  defects 
can  always  be  placed,  and  the  rapid  location  of 
faults  cannot  be  done  except  by  an  experienced 
person. 


CHAPTEK  YII 

DYNAMOS    AND    MOTOKS 

DURING  the  last  thirty  years  of  the  nineteenth 
century  the  practical  application  of  electricity  to 
the  uses  of  man  advanced  by  leaps  and  bounds ; 
and  it  is  safe  to  say  that  so  great  a  proportion  of 
this  advancement,  as  to  leave  but  an  insignificant 
remainder,  is  due  to  the  development  of  the 
dynamo  and  the  discovery  of  its  convertibility 
into  a  motor.  The  dynamo  has  rendered  it  pos- 
sible to  produce  currents  of  an  intensity  pre- 
viously undreamed  of  and  at  an  expense  so  far  be- 
low that  of  a  similar  generation  by  batteries  as 
to  put  the  latter  entirely  out  of  consideration  as 
a  competitor.  It  is  the  dynamo  that  is  now  de- 
pended upon  for  the  generation  of  all  currents 
aside  from  the  light  and  isolated  instances  that 
we  have  been  heretofore  considering. 

The  dynamo  has  converted  the  generation  of 

the  electric  current  from  a  matter  of  chemical 

combinations  to  the  mere  mechanics  of  motion. 

While  the  practical  working  of  the  dynamo  has 

100 


Bgnamos  ant)  /factors  107 

developed  many  difficulties  and  troubles  which  it 
has  taken  some  time  and  considerable  ingenuity 
to  overcome,  the  fundamental  principles  of  its 
operation  are  exceedingly  simple. 

It  has  already  been  shown  that  if  a  magnet  be 
made  to  approach  toward  or  recede  from  a  coiled 
wire,  or  to  pass  through  the  opening  of  its  coils, 
an  electric  current  will  be  generated  and  made 
to  pass  through  the  wire.  And,  further,  that  the 
strength  of  this  current  will  depend  upon  the 
power  of  the  magnet  and  the  form  and  number 
of  the  coils.  Hence  it  must  be  apparent  that  if 
a  coil  of  wire  be  made  to  approach  and  recede 
from  a  magnet  or,  in  other  words,  to  move  to 
and  fro  in  a  magnetic  field,  the  result  will  be  the 
same  as  though  the  coil  were  to  be  held  station- 
ary and  the  magnet  moved. 

As  revolution  about  a  shaft  in  a  magnetic  field 
is  the  easiest  method  of  accomplishing  this  result, 
this  is  the  way  in  which  the  work  has  been  done. 
The  dynamo,  then,  is  so  constructed  that  coils  of 
wires  are  revolved  in  front  of  the  faces  of  pow- 
erful magnets.  The  effect  of  this  work  done  in 
the  magnetic  field  is  to  generate  the  currents 
which  are  then  led  off  and  made  to  perform  use- 
ful work. 

In  order  to  obtain  the  maximum  results  with 


108  jeiectricits 

machinery  of  the  most  compact  form,  several 
coils  of  wire  are  moved  in  unison  between  the 
faces  of  two  magnets  that  are  set  opposite  to 
each  other.  The  result  of  this  is  that  there  are 
always  two  coils,  (those  nearest  the  faces  of  the 
magnets)  in  which  the  maximum  currents  are  be- 
ing generated. 

If  now  we  conceive  of  a  coil  of  wire  moving 
between  two  magnets  whose  north  and  south 
poles  are  presented  to  each  other,  it  will  be  ap- 
parent that  it  will  be  subjected  to  different  in- 
fluences as  it  passes  next  to  the  two  poles  respect- 
ively. This  difference  of  influence  will  produce 
different  results,  which  are  simply  that  the  cur- 
rent generated  in  the  coil  will  flow  in  one  direc- 
tion in  front  of  one  pole  and  in  the  other  direc- 
tion in  front  of  the  other  pole.  If  this  is  so,  there 
must  be  some  point  where  the  current  changes 
its  direction  of  flow,  and  this  must  occur  twice  in 
each  revolution  of  the  coil. 

It  has  also  been  shown  that  the  intensity  of 
the  current  depends  upon  the  intensity  of  the 
magnetic  field,  and  as  this  is  most  intense  directly 
in  front  of  the  centre  of  the  pole,  it  naturally 
follows  that  the  current  in  the  coil  gradually  in- 
creases in  intensity  from  one  neutral  point  to  the 
point  of  maximum  intensity  and  then  as  grad- 


2>Enamos  anfc  dfcotors  109 

ually  dies  away  to  the  other  neutral  point,  where 
reversal  takes  place  to  repeat  the  same  phenom- 
enon back  to  the  original  neutral  point. 

Having  generated  the  current  it  remains  to 
lead  it  off  and  make  it  available,  and  this  is 
purely  a  problem  of  mechanics. 

The  coils  are  wound  about  a  soft  iron  core  as 
shown  in  Fig.  30.  If  there  are  two  coils  on  this 
core  there  will  be  two  breaks  in  the  current  at 
each  revolution.  If,  however,  four  segments  or 
coils  are  used  the  current  will  be  continuous  in 
the  sense  that  there  is  no  actual  break  but  there 
will  be  a  variation  in  the  intensity  dependent 
upon  the  point  occupied  by  the  coils  in  the  rev- 
olution. This  variation  is  lessened  by  increasing 
the  number  of  coils,  still  more,  thus  holding  the 
current  at  a  constant  degree  of  intensity. 

As  it  is  impossible  to  graphically  represent  the 
wiring  of  a  large  number  of  segments  or  coils  as 
they  are  put  upon  a  single  armature,  attention  is 
particularly  directed  to  the  two-coil  arrangement 
shown  in  Fig.  30. 

The  current  generated  in  the  top  coil,  for  ex- 
ample, flows  in  the  direction  indicated  by  the 
arrows,  and  out  at  the  block  A  of  the  commutator. 
This  block  is  connected  to  the  block  B  by 
the  brushes  and  the  line  wire  so  that  the  cur- 


110 


Electricity 


rent  is  entering  from  B  and  flowing  into  the 
coils. 

The  commutator  is  formed  of  a  large  number 
of  copper  segments  placed 
radially  to  the  shaft  and  in- 
sulated from  it  and  from 
each  other. 

They  are,  in  fact,  the 
terminals  of  the  armature 
coils.  They  are  connected 
to  each  other  and  the  circuit 
thus  closed  through  the  in- 
termediary of  the  brushes. 
These  brushes  consist  of 
blocks  of  hard  carbon  or 
copper  that  can  be  adjusted 
to  come  into  contact  with  the  commutator  at 
the  proper  point  and,  while  insulated  from  the 
body  of  the  machine,  are  electrically  connected 
to  the  line  wires  to  which  they  deliver  the  cur- 
rent generated  in  the  armature. 

This  current  is  also  led,  either  in  whole  or  in 
part  through  the  field  magnets,  as  those  magnets 
between  which  the  armature  is  revolved  is  called, 
and  which  therefore  serve  for  their  own  excita- 
tion. 
It  might  properly  be  asked,  if  the  genera- 


FIG.  30.— DIAGRAM  OF 
ARMATURE  WIND- 
INGS FOR  DYNAMOS 


JDgnamos  anfc  Motors  in 

tion  of  the  current  is  due  to  the  presence  of  a 
magnet  outside  the  armature,  how  it  happens,  if 
this  magnet  depends  upon  the  current  for  its  own 
existence,  that  the  current  can  be  started  in  the 
first  place.  The  reason  lies  in  the  fact  that  there 
are  traces  of  magnetism  to  be  found  in  all  pieces 
of  iron,  and  especially  those  that  have  once  been 
magnetized,  known  as  residual  magnetism,  and  it 
is  this  faint  trace  that  serves  to  generate  the  first 
feeble  currents  that  make  themselves  manifest 
when  the  armature  is  set  in  revolution.  These 
at  once  serve  to  increase  the  magnetic  properties 
of  the  field  magnets  and  by  the  time  the  machine 
is  running  at  its  normal  speed  the  full  current 
for  which  it  was  wound  is  being  generated. 

In  order  to  understand  the  construction  and 
operation  of  the  dynamo,  it  will  be  well  to  pass 
in  brief  review  the  materials  that  are  used  and 
the  methods  that  are  followed  in  its  construction. 

The  armature  shaft  should  be  of  steel  and  of 
ample  strength  to  withstand  the  torsional  stresses 
that  are  put  upon  it.  And  it  must  be  remem- 
bered that  this  armature  shaft  has  real  work  to 
do  and  real  resistances  to  overcome.  The  coils 
of  the  armature  exert  a  push  contrary  to  their 
motion,  which  must  be  overcome,  and  all  of  the 
work  which  the  electric  current  generated  by  the 


112  ^Electricity 

dynamo  may  afterwards  be  called  upon  to  per- 
form, such  work  as  the  driving  of  machinery  or 
the  moving  of  street  cars,  must  be  done  and 
done  with  a  loss  of  about  35  per  cent,  by  the  ar- 
mature shaft. 

As  in  all  other  electrical  appliances  with 
which  we  have  had  to  deal,  copper  wire  is  used 
for  the  winding  of  the  armature.  This  wire  is 
invariably  insulated  with  some  covering  that  is 
not  likely  to  become  injured  by  heat  or  friction. 
A  good  cotton-covered  wire  of  about  16  guage  is 
a  suitable  one  for  small  dynamos.  In  the  laying 
of  this  wire  about  the  cores  the  utmost  care  must 
be  taken  that  it  is  immovably  packed  and  held  in 
position.  There  is  nothing  more  disastrous  to 
the  working  of  the  armature  than  loose  wires. 
We  have  already  seen  how  the  coils  oppose  a  re- 
sistance to  the  motion  of  revolution  that  is  im- 
parted to  them,  and  this  opposition  characterizes 
the  action  of  each  individual  wire,  with  the  re- 
sult that  it  tends  to  crowd  back  and  rub  upon  its 
fellow.  Then,  when  rubbing  does  take  place, 
the  insulation  is  soon  worn  away,  the  wires  of 
the  coil  come  into  contact  with  each  other,  short 
circuiting  and  heating  take  place  and  in  a  flash 
the  armature  is  frequently  ruined. 

The  core  of  the  armature  should  invariably  be 


Dynamos  anfc  /footers  113 

made  of  the  softest  and  purest  iron  that  is  ob- 
tainable. Cast  iron  will  not  do  at  all  and  forged 
wrought  iron  will  not  give  satisfactory  results. 
The  best  method  of  forming  the  core  is  to  build 
it  up  of  thin  plates  cut  out  of  refined  sheet  iron. 
The  reason  for  this  lies  partly  in  the  greater 
purity  of  the  metal  obtainable  and  partly  from 
the  fact  that  the  several  parts  can  be  insulated 
from  each  other.  Wires  may  also  be  successfully 
used  for  the  building  up  of  the  armature  core, 
but  the  mechanical  difficulties  of  handling,  join- 
ing and  insulating  them  makes  the  flat  plate  pref- 
erable. 

The  solid  iron  cores  are  objectionable  princi- 
pally upon  the  ground  of  their  tendency  to  heat, 
and  the  facility  with  which  they  permit  of  the 
formation  of  electrical  eddies,  known  as  Fou- 
cault  currents  within  their  confines. 

The  commutator  to  which  the  ends  of  the  coils 
are  attached  is  formed  of  a  number  of  copper 
segments  set  radially  about  the  shaft  and  insu- 
lated from  it  and  from  each  other.  They  are 
equal  in  number  to  the  coils  in  the  armature 
core. 

The  brushes  have  taken  almost  every  conceiv- 
able form  and  still  show  wide  variations,  de- 
pendent upon  the  ideas  of  the  manufacturer  or 


114  BlectrtcftB 

designer  of  the  machine.  They  may  be  a  bundle 
of  copper  wires,  soldered  together  at  one  end,  or 
thin  plates  of  the  same  metal  also  fastened  to- 
gether at  one  end,  or  a  plate  split  into  several 
tongues  by  slots  cut  into  the  end  or  pieces  of 
hard  carbon  with  an  electro-plated  covering  at 
the  end  and  extending  well  down  to  the  point  of 
contact  with  the  commutator,  where  bj  the  re- 
sistance of  the  mass  to  the  flow  of  the  electric 
current  is  greatly  diminished. 

The  field  magnets  are  usually  of  cast  iron 
though  sometimes  they  are  forged.  They  must 
be  wound  with  a  well-insulated  wire  which  may 
be  somewhat  larger  than  that  used  on  the  ar- 
mature. In  the  winding,  the  coils  should  be 
carefully  packed  but  there  is  not  the  same  tend- 
ency to  move  to  be  guarded  against  as  in  the 
armature.  As  a  matter  of  detail  it  is  well  to  put 
more  wire  about  the  central  portion  than  at  the 
ends,  as  contributive  to  a  greater  uniformity  of 
current. 

The  principle  of  action  of  the  dynamo  has 
been  seen  to  be  that  of  the  generation  of  an  elec- 
tric current  by  the  movement  of  a  coil  of  wire 
through  a  magnetic  field,  a  principle  that  was 
discovered  by  Faraday  in  1831. 

The  converse  of  this  is  also  true  that  if  an 


Dynamos  an&  dBotors  us 

electric  current  be  passed  through  a  coil  standing 
in  a  magnetic  field  there  will  be  a  tendency  to 
move.  This  movement  will  take  place,  however, 
in  a  direction  opposite  to  that  in  which  it  would 
be  necessary  to  move  the  coil  in  order  to  gener- 
ate a  current  similar  to  the  one  referred  to. 

This  converse  action  is  the  reason  for  what  is 
known  as  the  reversibility  of  the  dynamo. 
Hence  if,  instead  of  revolving  the  armature  by 
some  outside  power,  and  thus  generating  a  cur- 
rent, that  same  current  be  sent  into  the  armature, 
through  the  brushes  and  commutator,  it  will  re- 
volve in  the  opposite  direction  from  that  in 
which  it  would  itself  have  to  be  moved  when 
acting  as  a  dynamo  or  generator. 

The  dynamo  can,  then,  be  used  as  a  motor  or 
the  motor  as  a  dynamo  without  any  change 
whatever  in  construction.  As  a  matter  of  fact, 
however,  slight  changes  are  made  in  the  details 
of  construction  of  the  two,  in  order  that  each 
may  be  best  adapted  to  the  purposes  which  it  is 
called  upon  to  serve.  The  principle,  neverthe- 
less, remains  unchanged  and  is  merely  an  ex- 
ample of  reciprocal  action. 

Any  one  who  expects  to  operate  a  motor  or 
dynamo  should  have  this  elementary  knowledge 
of  their  construction  and  mode  of  action  in  order 


116  Blectrfcfts 

that  they  may  be  handled  intelligently.  This  is 
necessary  because,  like  all  other  machinery,  the 
dynamo  and  motor  have  their  ills  and  the  person 
who  has  charge  of  them  should  so  thoroughly 
understand  their  construction  that  it  will  be  pos- 
sible to  analyse  the  trouble  and  either  apply  a 
remedy  or  make  the  repairs  without  calling  in 
outside  assistance. 

As  the  dynamo  and  motor  are  so  nearly  iden- 
tical, they  will  be  considered  collectively  here- 
after under  the  general  title  of  "  machine." 

In  the  selection  of  an  electric  machine,  the 
same  advice  may  be  given  as  in  the  case  of  the 
battery.  Be  sure  and  secure  one  that  has  an 
ample  margin  of  excess  above  the  calculated  re- 
quirements of  the  work  in  hand.  It  is  a  peculiar 
property  of  the  machine  that,  whether  working 
as  a  generator  or  a  motor,  it  automatically  ad- 
justs itself  to  the  amount  of  work  that  it  has  to 
do.  Thus  the  dynamo  will  generate  no  more 
current  than  is  being  drawn  off  from  the  line, 
and  it  will  generate  as  much  as  the  demand  re- 
quires, even  to  the  point  of  overheating  and 
burning  out.  So,  too,  the  motor  will  take  in 
only  the  amount  of  current  required  for  its 
work,  but  when  the  latter  is  increased  too  far 
beyond  its  rated  capacity,  it,  too,  will  struggle 


2>£namo6  anb  Motors  117 

to  meet  the  demand,  even  to  the  point  of  a  col- 
lapse. 

For  these  reasons  it  is  well  to  have  an  excess 
of  power  in  reserve,  that  overloading  may  be 
avoided.  As  a  matter  of  fact  it  is  probable  that 
in  nine  cases  out  of  ten,  a  machine  will  run  more 
economically  when  its  output  is  twenty  per  cent, 
less  than  its  rated  capacity  than  when  run  up  to 
the  limits  of  that  capacity. 

Another  point  in  the  selection  of  the  machine 
should  be  borne  in  mind  and  that  is  that  there 
is  no  economy  in  the  purchase  of  cheap,  light 
machines.  The  purity  of  the  metal  required  in 
their  construction  and  the  care  that  must  be 
taken  in  the  workmanship  makes  them  more  ex- 
pensive to  manufacture  than  other  classes  of  ma- 
chinery of  the  same  weight.  Hence  a  low  price 
usually  means  the  neglect  of  some  essentials. 

Weight,  besides  being  of  value  from  an  elec- 
trical standpoint,  is  also  an  advantage  in  that  it 
serves  to  steady  the  running ;  and  this  is  a  most 
important  factor  in  the  operation  of  any  elec- 
trical machine. 

After  the  machine  has  been  selected  it  should 
be  carefully  located  and  set.  The  principal  point 
in  this  is  to  see  that  the  foundation  or  base  upon 
which  it  is  placed,  is  solid  and  unyielding.  If 


118  BiectrfcttB 

the  machine  is  a  small  one,  there  will  be  no  need 
to  build  a  special  foundation.  But,  even  though 
it  be  merely  a  desk  fan,  it  should  be  put  where 
it  will  be  steady  and  not  subjected  to  jars.  Large 
machines  should  be  placed  upon  special  masonry 
foundations. 

The  direction  of  rotation  of  a  motor  depends 
upon  the  direction  of  the  flow  of  current  through 
it.  This  must  be  evident  from  the  principles  of 
its  action  as  already  laid  down.  A  current  flow- 
ing in  one  direction  through  its  coils  will  tend  to 
move  them  in  one  direction,  and  in  another  if  it 
is  reversed. 

Ordinarily,  electric  machines  are  intended  to 
run  right-handed,  that  is,  from  left  over  to  right, 
or  in  the  direction  of  the  movement  of  the  hands 
of  a  watch,  when  the  observer  is  standing  at  the 
pulley  end  of  the  armature  shaft.  They  can, 
however,  be  made  to  run  in  the  opposite  direc- 
tion by  merely  reversing  the  position  of  the 
brushes.  When  this  is  done  on  an  ordinary 
two-pole  machine,  no  other  connection  need  be 
changed.  This  merely  changes  the  direction  of 
rotation  and  the  position  of  the  brushes. 

It  must  not  be  thought  that  changing  the  con- 
nection of  the  wires  will  effect  the  same  result. 
This,  to  be  sure,  changes  the  direction  of  the 


an&  /footers  119 

current  in  the  coils,  but  it  does  the  same  thing 
for  the  field  magnets  thus  changing  their  polarity, 
or  converting  what  was  the  north  pole  to  the 
south  pole  and  vice  versa,  and  thus  keeping  the 
direction  of  rotation  the  same.  The  only  way 
in  which  this  can  be  done  is  to  change  the  direc- 
tion of  the  flow  of  the  current  in  the  field  or  the 
coils  alone. 

Before  starting  any  electric  machine  it  should 
be  thoroughly  inspected  to  make  sure  that  it  is 
in  perfect  working  order.  This  means  that,  first 
of  all,  it  should  be  clean.  All  dust  and  grit  and 
especially  all  metallic  particles  should  be  wiped 
off,  lest  they  cause  a  short  circuiting,  and  above 
all  should  this  be  done  in  connection  with  the 
commutator  and  brushes. 

The  actual  starting  should  be  done  slowly  and 
with  a  watchfulness  that  will  make  it  possible  to 
stop  at  once,  if  anything  goes  wrong.  The  shaft 
should  be  examined  to  see  that  it  moves  freely 
in  its  bearings,  and  the  lubricators  be  adjusted 
to  feed  the  oil  properly. 

A  word  of  caution  may  be  interjected  here  to 
those  who  are  called  upon  to  handle  electric  cur- 
rents. Do  not  touch  a  conductor  with  the  bare 
hands.  Do  not  attempt  to  manipulate  conductor 
wires  with  ordinary  tools.  Always  wear  rubber 


120  Electricity 

gloves,  and  rubber  shoes  are  also  a  wise  extra 
precaution.  Always  use  tools  that  have  insul- 
ating handles  when  at  work  about  electric  ma- 
chines or  wires  where  the  voltage  is  high.  It  is 
well,  also,  to  work  with  one  hand  only,  so  that 
in  case  of  accidental  contact  the  current  will  not 
pass  from  one  side  to  the  other  of  the  body. 

After  a  machine  has  been  at  work  for  some 
time  it  frequently  happens  that  it  causes  a  good 
deal  of  trouble  by  sparking  at  the  brushes.  This 
sparking  may  take  the  form  of  a  vivid  flash  of 
light  that  hovers  constantly  about  the  point  of 
contact  as  a  bluish  flame  or  it  may  be  inter- 
mittent. There  are  several  causes  for  this,  one 
of  the  principal  being  failure  of  contact  between 
the  brush  and  the  commutator.  This  may  be 
due  to  an  unevenness  in  the  surface  of  the  com. 
mutator  as  the  result  of  wear ;  or  the  brush  itself 
may  be  so  hard  that  it  will  not  work  down  to  a 
good  surface ;  or  the  machine  may  be  vibrating 
to  such  an  extent  that  the  jar  is  communicated 
to  the  brushes.  Sparking  may  also  result  from 
the  brushes  being  out  of  position,  a  broken  cir- 
cuit in  the  armature,  weak  field  magnetism  or  a 
high  resistance  in  the  brush. 

There  is  then  an  apparently  wide  field  for  in- 
vestigation when,  sparking  occurs  at  the  brushes 


Bgnamos  and  /footers  121 

though  each  of  the  mechanical  difficulties  show 
at  once  whether  or  not  they  are  the  causes  of  the 
trouble.  In  a  well-designed  and  well-built  ma- 
chine that  has  been  well  cared  for  and  not  over- 
loaded, the  chances  are  that,  in  ninety-nine  cases 
out  of  a  hundred,  the  cause  will  be  found  in  some 
trouble  with  the  brushes  or  unevenness  in  the 
worn  surface  of  the  commutator. 

Owing  to  the  character  of  the  insulation  used, 
it  is  very  desirable  that  the  armature  and  field 
magnets  should  run  cool,  and  they  must  be  care- 
fully watched  to  see  that  this  condition  is  main- 
tained. The  heating  of  the  armatures  may  result 
from  moisture  that  has  soaked  in  among  the 
coils,  from  an  excess  current  passing  through  it 
or  from  short  circuiting.  The  Foucault  currents 
due  to  a  solid  ring  construction  will  also  produce 
this  result,  and  it  sometimes  happens  that,  in 
winding  an  armature,  one  or  more  coils  are  con- 
nected in  the  wrong  direction.  When  either  of 
these  constructional  difficulties  is  the  cause  of 
the  heating,  there  is  no  remedy  other  than  in  a 
rebuilding  of  the  armature.  Heating  of  the 
field  magnets  may  also  be  due  to  moisture  in  the 
coils,  excess  of  current  or  Foucault  currents. 
The  first  can  be  cured  by  drying,  in  the  second 
it  may  be  due  to  a  short  circuit  in  one  coil,  thus 


122  Electricity 

sending  an  excess  into  the  other,  and  in  the  last 
the  remedy  again  lies  only  in  reconstruction. 

These  are  merely  a  few  of  the  more  prominent 
troubles  that  are  apt  to  arise  in  the  care  of  elec- 
trical machinery.  But,  like  all  apparatus  of  its 
kind  there  are  always  unexpected  developments 
that  must  be  met  with  a  knowledge  of  the  prin- 
ciples in  accordance  with  which  the  machine  is 
constructed.  And,  while  this  is  simple  in  itself, 
there  are  so  many  outside  variables  that  come  in 
to  influence  its  action  that .  the  result  is  one  of 
some  complication,  though  by  no  means  impos- 
sible of  solution  by  any  one  who  will  take  the 
pains  to  examine  into  the  several  phenomena  as 
they  manifest  themselves  in  the  course  of  ex- 
perience. 

It  is  due  to  the  dynamo  and  its  reversibility  as 
a  motor  that  the  electrical  progress  of  the  last 
quarter  o.f  a  century  is  due  and  the  former  has 
stepped  in  to  supply  electric  currents  on  a  scale 
that  would  be  utterly  impracticable  were  reliance 
to  be  placed  upon  batteries.  It  has  enabled  the 
telegraph  companies  to  meet  the  demands  that 
have  been  made  upon  them  for  an  increase  of 
service,  while  the  applications  for  the  develop 
ment  of  light,  heat  and  power  may  be  numbered 
by  the  thousands. 


CHAPTEE  VIII 

ELECTEIC   LIGHTING 

IT  has  been  shown  in  a  previous  chapter  that 
all  substances  offer  a  certain  definite  amount  of 
resistance  to  the  passage  of  the  electric  current. 
This  resistance  is  least  in  silver,  a  trifle  more  in 
copper,  still  more  in  iron  and  the  increase  con- 
tinues on  through  other  substances,  being  very 
great  in  glass  and  air.  In  overcoming  these  re- 
sistances heat  is  generated  and  this  heat  is  in  pro- 
portion to  the  resistance  and  the  intensity  of  the 
current.  With  the  good  conductors  such  as 
copper  and  iron  the  temperature  is  rarely  raised 
to  such  a  degree  that  the  metal  becomes  red  hot 
except  in  the  case  of  currents  of  great  in- 
tensity. 

This  generation  of  heat  is  shown  in  the  results 
of  a  stroke  of  lightning,  where  buildings  may  be 
set  on  fire  on  account  of  the  resistance  of  the  ma- 
terial to  the  passage  of  the  current. 

This  principle  is  made  use  of  in  all  systems  of 
electric  lighting  whether  it  be  arc  or  incandes- 

123 


124 

cent.  The  practical  method  by  which  the  re- 
sults are  obtained,  is  to  interpose  some  substance 
of  such  high  resistance,  that  it  is  heated  by  the 
passage  of  the  current  to  an  incandescent  condi- 
tion. The  development  of  heat  invariably  pre- 
cedes the  appearance  of  light  and  the  time  re- 
quired is  also  a  matter  of  material  and  strength 
of  current. 

The  material  that  is  apparently  best  adapted 
for  use  in  the  electric  lamp  seems  to  be  some 
form  of  carbon.  In  what  is  known  as  the  arc 
light  there  is  an  actual  consumption  of  the  car- 
bon ;  whereas,  in  the  incandescent  system,  there 
is  theoretically  no  such  consumption. 

The  fact  that  an  intensely  bright  light  could  be 
produced  by  the  passage  of  an  electric  current 
through  two  carbon  points  was  discovered  by 
Sir  Humphrey  Davy  in  1813,  who  used  a  battery 
of  2,000  voltaic  cells  for  the  generation  of  his 
current,  and  two  sticks  of  common  wood  char- 
coal for  the  electrodes. 

The  carbon  used  for  the  present  arc  light  is  a 
manufactured  article  that  is  very  hard.  The 
original  carbons  used  by  Davy  were  soft  and 
were  rapidly  wasted  away  in  service.  It  there- 
fore became  necessary  to  secure  something  that 
would  retain  its  shape  and  burn  slowly.  This  has 


JElectrfc  SLfsbtfns  125 


been  found  in  the  Carre  carbons  which  may  be 
made  as  follows  : 

"  Fifteen  parts  of  pure  coke  finely  pulverized 
and  five  parts  of  calcined  lamp-black,  are  mixed 
with  seven  to  eight  parts  of  a  syrup  made  of 
cane  sugar  and  gum  arabic,  in  the  proportion  of 
thirty  parts  of  sugar  to  ten  parts  of  gum.  The 
mixture  is  then  pulverized,  made  into  paste  with 
water,  forced  under  heavy  pressure  into  a  die 
form  required  for  the  carbons,  and  baked  re- 
peatedly at  a  very  high  temperature.  After 
each  baking  the  carbons  are  immersed  in  a  con- 
centrated syrup  of  burnt  sugar,  maintained  at  a 
boiling  temperature,  so  as  to  fill  the  pores  with  the 
sugar,  the  process  being  facilitated  by  intervals 
of  cooling  ;  and  the  superfluous  syrup  being  washed 
from  their  surfaces  with  boiling  water  previous  to 
each  baking.  When  the  required  density  has  been 
obtained,  the  carbons  are  slowly  dried  for  about 
fifteen  hours  at  a  temperature  of  about  340°  Fahr., 
and  they  are  then  ready  for  use." 

The  carbons  are  then  given  a  coating  of  copper 
by  electro-plating  so  as  to  reduce  the  resistance 
over  a  greater  portion  of  the  stick  from  that  of 
carbon  to  copper.  When  so  made  they  are  very 
strong  and  are  used  in  lengths  of  from  18  inches 
to  20  inches. 


126 

Great  as  may  be  the  resistance  of  the  carbon^ 
that  of  the  air  is  still  greater  and  it  is  necessary, 
in  order  to  produce  an  arc  light  that  the  two 
pieces  should  first  be  in  contact  and  then,  after 
the  flow  of  the  current  is  established,  be  drawn 
apart.  The  current  thus  started  while  the  car- 
bons are  in  contact  leaps  across  the  air  space  in- 
terposed when  they  are  drawn  apart  and  the 
intensity  of  the  heat  thus  generated  maintains 
the  light. 

For  convenience  the  carbons  are  usually  set  in  4 
a  vertical  position  with  the  current  entering  at 
the  upper  one,  which  thus  becomes  the  positive 
electrode  of  the  lamp.  As  this  upper  carbon 
burns  away  it  assumes  the  form  of  a  truncated 
cone  or  crater,  while  the  lower  one  becomes 
pointed.  The  space  between  is  filled  with  a 
mixture  of  carbon  vapor  and  air,  which,  at  the 
high  temperature  at  which  it  is  maintained,  has 
a  much  lower  resistance  than  the  air  at  ordinary 
temperatures.  Both  points  are  maintained  at  a 
white  heat  and  it  is  the  radiation  from  these  in- 
candescent tips  that  produces  the  light.  Of  the 
two,  the  condition  of  the  upper  one  is  the  most 
intense  and  is  really  the  source  of  about  sixty- 
five  per  cent,  of  all  the  light  radiated  by  the 
lamp. 


Electric  Xfgbtfng 


127 


Of  course  it  is  necessary  that  the  bringing  of 
the  carbons  into  contact  in  an  extinguished  lamp 
and  their  separation,  immediately  the  flow  of 
current  has  been  started,  should  be  done  automat- 
ically. There  have  been  a  great  variety  of 
lamps  brought  out  for  this  purpose  in  which  ad- 
vantage is  taken  of  the  variation  in  the  resistance 
offered  by  car- 
bons in  contact  / "  X.  ^  /  n  / 
and  apart.  Some  >\  T^>3®mm~^  "  / 
of  these  lamps 
are  of  compli- 
cated construc- 
tion and  involve 
the  use  of  more 
or  less  clock- 
work. Among 
the  simplest  is 
the  Brush  lamp  that  will  serve  to  show  the 
method  of  operation  employed. 

This  lamp  depends  for  its  working  upon  the 
action  of  a  solenoid,  or  a  soft  iron  core  free  to 
move  in  a  coil  of  wire  through  which  an  electric 
current  is  passing. 

The  construction  of  the  Brush  lamp  is  shown 
in  Fig.  31.  The  carbons  are  represented  by  A-j- 
and  A —  respectively.  The  terminals  of  the  line 


FIG.  31. — DIAGEAM  OF  BRUSH  ABC 
LAMP 


128  Blectticfts 

circuit  are  at  B  and  C.  The  lower  carbon  is  held 
in  a  stationary  frame  that  is  in  direct  electrical 
contact  with  the  terminal  C.  The  upper  carbon 
is  held  in  a  washer  D  that  is  clutched  by  an  ex- 
tension from  the  base  of  the  solenoid  E.  The 
main  wire  leading  oif  from  the  terminal  B  is 
divided  into  three  parts.  One  part  F  leads  down 
through  the  resistance  coil  E-  to  the  armature  G  of 
the  magnet  H,  whose  uses  will  be  explained  later. 
The  other  two  branches  I  and  K  pass  through  the 
coils  L  and  M  of  the  solenoids  and  then  uniting 
are  led  to  a  contact  with  the  upper  carbon  at  N. 

In  addition  to  this  a  main  wire  is  led  down 
from  the  terminal  C  to  the  coil  H  and  ends  in  the 
contact  O. 

Another  finer  wire  P  is  led  between  the  ter- 
minals B  to  C,  around  the  coils  H,  L  and  M,  but  in 
an  opposite  direction  to  these  coils.  This  wire 
is  what  is  known  as  a  shunt  circuit  and,  owing 
to  its  greater  resistance,  carries  only  about  one 
per  cent,  of  the  total  current,  but  by  giving  it  a 
greater  number  of  coils  about  H,  L  and  M  it  serves 
to  materially  modify  and  counteract  the  magnet- 
izing properties  of  those  coils. 

When  the  lamp  is  to  be  lighted  a  current  is 
allowed  to  pass  from  the  terminal  B  to  C.  In 
doing  so  it  flows  through  the  coils  L  and  M  and 


Electric  Xisbting  129 


the  two  carbons.  The  resistance  of  the  latter 
being  comparatively  little  the  solenoid  cores  rise 
through  the  coils  L  and  M  and  separate  the  car- 
bons producing  the  light.  As  the  distance  of  this 
separation  increases  so  does  the  resistance,  thus 
checking  the  flow  of  the  current  and  correspond- 
ingly weakening  the  strength  of  the  solenoid. 
The  latter  then  drops  back  until  it  reaches  the 
point  where  the  weight  and  strength  of  the 
solenoid  are  balanced,  and  the  lamp  continues  to 
work  in  this  its  normal  position. 

The  wire  F  leading  to  the  resistance  coil  K  is 
to  enable  the  lamp  to  automatically  close  the 
circuit  between  B  and  C  in  case  of  accident  and 
thus  prevent  other  lamps,  that  are  in  circuit  in 
series  with  it,  from  becoming  extinguished. 
When  an  accident  resulting  in  the  permanent 
extinguishment  of  the  lamp  ocpurs  this  circuit  so 
magnetizes  the  core  of  H  that  the  armature  G  is 
attracted  and  the  contact  points  O  are  brought 
together,  thus  permitting  a  direct  flow  of  the 
current  from  B  to  C  through  the  resistance  coil  li 
which  now  takes  the  place  of  the  lamp  in  inter- 
posing the  proper  resistance  into  the  circuit. 

The  arc  lamp  properly  constructed  is  capable 
c?  emitting  an  intense  light  ranging  from  an  or- 
dinary lamp  of  1,200  candle  power  to  the  most 


130  Electricity 

powerful  search  lights  of  50,000  candle  power  or 
more.  The  current  of  course  varies  with  the  in- 
tensity of  the  light  and  is  approximately  about 
one  two-hundredths  of  the  same.  Thus  for  a 
1,200  candle  power  light  about  6.8  amperes  of 
current  will  be  required ;  for  2,000  candle  power 
about  10  amperes  and  so  on,  decreasing  slightly 
in  proportion  to  the  increase  of  light. 

At  present  the  current  used  for  electric 
lighting  is  generated  by  the  dynamo,  and  indeed 
it  was  the  discovery  and  development  of  the 
latter  that  has  rendered  the  method  possible. 
"While  it  is  quite  feasible  to  generate  a  current 
with  batteries  alone,  that  are  capable  of  main- 
taining an  arc  light,  their  bulkiness,  first 
cost  and  expense  of  maintenance  place  them 
quite  outside  the  pale  of  any  commercial  con- 
siderations. 

As  the  arc  lamp  continues  in  use,  the  carbons 
gradually  waste  away  and  must  be  renewed 
after  a  certain  length  of  time.  In  fact  they  are 
consumed  at  an  approximate  rate  of  about  \y2 
inches  per  hour. 

In  the  incandescent  lamp  we  have,  on  the 
other  hand,  an  example  of  a  resistance  coil  pure 
and  simple.  There  is,  to  be  sure,  a  slow  wasting 
away  and  gradual  deterioration  of  the  carbon  but 


Electric  ILfgbttns  isi 


no  consumption  that  is  comparable  to  that  of  the 
arc  lamp. 

The  incandescent  system  of  lighting  involves 
the  placing  of  a  section  of  high  resistance  in  the 
circuit.  The  current,  in  passing  through  this 
section  heats  it  and  raises  it  to  such  a^  condition 
of  incandescence  that  it  emits  light.  In  order 
that  this  resisting  section  may  be  made  small  and 
light  and  that  it  may  not  be,  at  the  same  time, 
burned  by  contact  with  the  oxygen  of  the  air, 
when  in  this  glowing  condition,  it  is  enclosed  in 
an  air-tight  bulb  from  which  the  air  has  been  ex- 
hausted so  that  the  work  is  done  in  a  partial 
vacuum  away  from  the  destructive  influences  of 
the  oxygen. 

The  filaments,  as  these  resisting  sections  pro- 
ducing the  light  are  called,  are  usually  made  of 
fine  threads  of  carbon.  They  are  exceedingly 
delicate  and  are  instantly  dissipated  if  a  crack  or 
leak  in  the  glass  bulb  admits  ever  so  small  a 
quantity  of  air. 

The  development  of  the  incandescent  light  has 
required  a  great  deal  of  experimenting  in  order 
to  secure  the  best  possible  material  for  use  in  the 
making  of  these  filaments  ;  and  the  several  manu- 
facturers have  each  a  material  that  is  used  for 
the  particular  lamp  made.  Edison  uses  a  bain- 


132  Blcctcicits 

boo  fibre  taken  from  the  interior  of  the  plant ; 
the  Lane-Fox  carbons  are  made  from  a  grass 
fibre  known  as  bass  broom ;  the  Cruto  carbons 
are  made  by  depositing  the  carbon  upon  a  fine 
platinum  wire  ;  the  Weston  carbons  are  made  of 
cotton  as  are  also  the  Swan. 

The  filament  is  almost  invariably  made  in  the 
form  of  a  horseshoe,  and  great  care  must  be  ex- 
ercised in  their  manufacture.  Its  resistance  de- 
pends, to  a  great  extent,  upon  its  length  and 
diameter.  An  ordinary  filament  would  be  about 
5  inches  long  and  .005  inch  in  diameter,  and  this 
would  be  suitable  for  a  lamp  of  sixteen  candle 
power.  The  wastage  of  the  filament  is  due  to 
the  actual  burning  away  of  the  carbon  caused  by 
the  presence  of  a  small  amount  of  oxygen  that  re- 
mains within  the  glass  on  account  of  the  impos- 
sibility of  producing  a  perfect  vacuum.  There  is 
also  a  certain  amount  of  wastage  as  the  result  of 
incandescence  in  which  infinitesimal  portions  of 
the  carbon  are  given  off  as  vapor  to  settle  again 
on  the  interior  of  the  glass,  whither  they  are  at- 
tracted by  the  difference  in  what  is  termed  the 
potential.  This  is  the  cause  of  the  darkening 
that  takes  place  in  incandescent  light  glasses 
after  they  have  been  in  use  for  a  time. 

It  may  be  explained  here  that  the  term  "  dif- 


Electric  Hfgbttng  133 

ference  of  potential"  is  used  to  express  technic- 
ally the  reason  for  the  flow  of  the  electric  cur- 
rent. At  the  positive  pole  of  the  battery  or 
dynamo,  it  is  supposed  that  there  is  a  higher 
pressure  or  potential  than  at  the  negative.  This 
difference  causes  a  flow  of  the  current  from  one 
pole  to  the  other.  It  is  analogous  to  the  flow  of 
water  through  a  pipe  which  takes  place  from  the 
point  of  greatest  pressure  to  the  least. 

The  voltage  used  in  incandescent  lighting 
covers  a  wide  range  of  from  50  to  120  volts,  with 
from  90  to  100  as  an  approximation  to  average 
practice.  "With  this  voltage  the  durability  of  a 
lamp  or  the  filament  will  be  from  600  to  1,000 
hours  of  service.  The  glass  or  bulb  is  so  fitted 
with  the  contact  points  that  when  it  is  screwed 
into  its  socket  it  automatically  makes  its  own 
connections  and  places  the  filament  in  the  circuit. 

The  methods  to  be  employed  in  the  placing  of 
electric  lights  and  the  wiring  for  the  same  are 
matters  of  interest  to  all  users.  All  wiring  for 
residences,  offices  or  factories  should  be  done  on 
one  of  the  two  systems  known  as  the  multiple 
arc  and  three-wire  systems. 

The  first  is  represented  in  Fig.  32.  Here  the 
current  generated  by  the  dynamo  at  A  flows  out 
at  the  positive  pole  and  over  the  wire  B.  This 


134  jeiectrtcfts 

wire  is  connected  to  the  return  wire  C,  leading  to 
the  negative  pole  of  the  dynamo,  by  a  number  of 
special  wires  in  each  of  which  there  is  placed  an 

incandescent 

0111111111111   lamp.     Each  of 
mmHHH  these     Umpa 

+  e  ,  .          -j 

FIG.  32. — MULTIPLE  ARC  SYSTEM  OF  IN-  ° 

CANDESCENT  LIGHTING  pendently  of  all 

of    the    others 

and  may  burn  out  or  become  destroyed  without 
affecting  the  action  of  the  others  in  any  way.  The 
two  essential  conditions  for  the  use  of  this  system 
are  that  the  dynamo  should  maintain  a  constant 
voltage  in  the  wires,  regardless  of  the  number  of 
lamps  in  use ;  and  that  only  lamps  intended  for 
the  same  voltage  shall  be  used. 

The  working  of  this  system  is  explained  as  fol- 
lows :  The  current  generated  by  the  dynamo 
flows  out  upon  the  wire  and  a  certain  portion  of 
it  cuts  across  to  the  return  wire  through  each  of 
the  lamp  circuits,  the  total  output  of  the  dynamo 
corresponding  to  the  number  of  lamps  in  service. 

In  order  to  lessen  the  work  of  the  dynamo  and 
for  other  reasons  it  is  sometimes  desirable  to  cut 
out  certain  lines  of  wire,  and  for  this  purpose 
switches  are  used.  In  electrical  parlance  a  switch 
may  be  defined  as  a  means  for  opening  or  closing 


Electric  3U0btfng  135 


a  circuit.  They  are  invariably  located  close  to 
the  dynamo  in  the  power  house  so  that  the  cur- 
rent can  be  cut  off  from  or  turned  into  certain 
lines.  It  is  always  well  to  have  them  arranged 
to  open  and  close  quickly  and  they  must  possess 
ample  capacity  to  carry  the  full  current  of  the 
line.  A  satisfactory  form  is  the  knife  switch  in 
which  a  blade  of  copper  is  made  to  enter  between 
two  others  thus 
closing  the  con- 
nection  ;  and  if 
the  moving  part 
is  made  so  as  to 
be  started  by  FJG>  33<_THEEE.WIEE  SYSTEM  OF  IN- 
hand  and  be  CANDESCENT  LIGHTING 

then  driven  in 

by  a  spring  it  will  be  better  on  account  of  the 
rapidity  of  its  movement.  Similar  switches 
should  also  be  placed  in  the  wires  as  they  enter 
buildings  and  at  all  points  beyond  which  the  in- 
stallation may  be  considered  as  separate.  This 
makes  it  possible  to  examine  and  repair  such 
parts  of  the  installation,  without  interfering  in 
any  way  with  the  working  of  other  parts. 

The  three-wire  system  is  shown  in  Fig.  33. 
The  advantage  of  this  method  is  one  that  affects 
the  producer  rather  than  the  consumer,  in  that 


136  Electricity 

its  advantage  lies  in  the  reduced  quantity  of  wire 
required  for  the  mains. 

The  dynamos  are  connected  in  series  as  shown, 
and  the  lamps  are  placed  in  a  circuit  interposed 
between  the  positive  and  negative  wires  A  and  B, 
and  a  neutral  wire  C.  When  an  equal  number  of 
the  lamps  in  the  two  lines  D  and  E  are  lighted  the 
current  flows  out  at  A,  cuts  across  to  the  return 
wire  B  through  the  lamps  and  so  back  to  the 
dynamos.  If,  however,  an  unequal  number  are 
in  use  in  the  two  lines,  the  third  wire,  which  was 
neutral  before,  now  comes  into  action  and  acts  as 
a  positive  or  negative  wire  according  as  the 
greater  number  of  lamps  are  burning  in  the  line 
E  or  D.  This  method  makes  it  possible  to  use 
three-eighths  the  amount  of  copper  in  the  mains 
that  the  two- wire  or  multiple  arc  system  would 
require  for  the  same  number  of  lamps. 

Where  the  wires  for  the  electric  lighting  of  a 
building  are  to  be  run  after  the  building  has  been 
erected  the  most  common  and  cheapest  method 
of  doing  the  work  is  to  use  cleats.  These  cleats 
consist  merely  of  short  strips  of  wood  with 
grooves  cut  across  one  face  of  a  proper  size  to 
receive  a  wire  and  hold  it  firmly  when  the  cleat 
is  nailed  or  screwed  against  a  ceiling  or  partition. 
The  same  precautions  as  to  the  tightening  of  the 


Electric  ftigbting  137 

wires  that  are  to  be  observed  in  other  classes  of 
wiring  must  be  followed  in  this. 

The  use  of  the  cleat  leaves  all  of  the  wires  ex- 
posed  to  view.  If  it  is  desired  to  have  them  con- 
cealed it  will  be  necessary  to  cut  holes  in  the 
plaster  at  the  point  where  it  is  desired  to  place 
the  lamp  and  run  the  wires  between  the  sides  of 
the  partitions  and  between  the  floors  and  ceilings 
to  the  source  of  supply.  To  do  this  successfully 
will  require  some  time  and  patience. 

Through  the  hole  in  the  wall,  which  should  be 
clear  of  the  studding,  drop  a  length  of  No.  19 
jack  chain  to  which  a  strong  string  is  attached. 
Locate  its  position  on  the  ceiling  by  jouncing  it 
with  the  string  and  then  bore  a  hole  through  an 
adjacent  base  board  and  fish  for  it  with  a  piece 
of  wire  having  a  hook  on  the  end.  Move  it  along 
from  point  to  point  in  this  way  and  draw  after 
it  the  wires  for  the  lamp. 

It  need  hardly  be  said  that  the  wire  used  for 
all  electric  lighting  purposes  must  be  covered 
with  some  good  insulation.  Some  one  of  the 
compositions  of  rubber  is  the  material  that  is 
usually  used  for  this  purpose.  The  greatest  earn 
must  be  exercised,  in  the  running  of  the  wires 
that  the  insulation  is  not  injured  in  any  way. 
This  is  particularly  true  of  concealed  work.  If 


138  Blectricfts 

the  wires  are  placed  after  the  completion  of  the 
building,  they  must  be  cautiously  handled  lest 
the  insulation  be  broken  or  torn  from  the  wire 
while  it  is  being  drawn  into  place.  If  the  work 
is  done  on  an  uncompleted  building,  eternal 
vigilance  alone  will  serve  to  guard  it  against  the 
carelessness  or  wilful  maliciousness  of  the  work- 
men engaged  in  the  construction.  The  cotton- 
wrapped  wire  that  can  be  used  for  bell  work 
should  not  be  employed  for  electric  lighting 
owing  to  the  danger  of  fire. 

In  additition  to  the  insulation  covering  the 
wire,  other  safety  devices  must  be  introduced 
into  the  system.  One  of  these  is  the  use  of  the 
safety  plug  or  fuse. 

There  is  always  present  the  possibility  of  an 
abnormal  increase  in  the  voltage  on  an  electric 
lighting  circuit,  which  might  heat  the  wires  to  a 
temperature  sufficient  to  set  fire  to  the  insulation 
or  other  materials  with  which  they  are  in  con- 
tact. The  fuse  may  be  attached  to  the  wires  by 
binding  screws,  so  as  to  be  easily  replaced  if 
melted,  and  are  so  constructed  that  they  will 
melt  and  thus  break  the  circuit,  before  the  wires 
will  become  sufficiently  hot  to  do  any  damage, 
and  this  should  be  limited  to  150°  Fahr. 

Again,  wherever  a  current  enters  a  building 


Electric  Xfgbtfns  139 


there  should  be  a  switch  where  the  connection 
can  be  broken  and  the  wires  thus  be  made  dead 
so  that  they  can  be  handled  with  impunity  for 
repairs. 

Wherever  wires  are  to  be  joined  the  splice 
should  be  made  in  accordance  with  the  direc- 
tions given  in  connection  with  Fig.  4  on  page  27. 
After  the  splice  has  been  made  it  should  be 
carefully  wrapped  and  thoroughly  protected  by 
means  of  adhesive  insulating  tape,  wound  tightly 
about  it.  This  should  be  carried  out  to  a  suffi- 
cient thickness  to  form  a  thorough  insulation, 
and  for  that  purpose  should  be  somewhat  thicker 
than  the  regular  insulation  about  the  wire.  The 
joints  should  also  be  soldered  before  winding. 

When  the  wires  pass  through  a  wall,  partition 
or  joist  an  extra  insulation  should  be  used.  This 
usually  takes  the  form  of  a  hard  rubber  or  com- 
position tubing  which  may  be  procured  at  any 
supply  store. 

The  size  of  the  wire  used  must  also  receive  its 
due  amount  of  attention.  Copper  is,  of  course, 
the  only  material  to  b.e  considered.  The  larger 
the  wire  the  greater  the  number  of  lamps  that  it 
will  carry.  Thus  a  No.  18  wire  will  carry  7 
lamps  of  55  volts  and  14  of  110  volts.  With  a 
No.  14  wire,  we  find  that  15  of  the  55-volt  and 


140  Electricity 

30  of  the  110-volt  lamps  can  be  carried.  With  a 
Ko.  8  wire,  these  figures  are  increased  to  40  and 
80  lamps  respectively. 

The  determination  of  the  size  of  wire  suited 
for  use  in  an  installation  is  a  matter  that  can  be 
readily  calculated.  The  resistance  of  a  wire  is 
dependent  upon  its  size,  and  this  is  usually  ex- 
pressed in  terms  of  "  circular  mils."  A  circular 
mil  may  be  defined  as  the  sectional  area  of  a 
wire  wThose  diameter  is  one-thousandth  of  an 
inch.  As  the  sectional  areas  of  wrires  vary  as 
the  squares  of  their  diameters,  it  follows  from 
this  that  a  wire  %  inch  in  diameter  will  contain 
62,500  circular  mils. 

The  problem  of  determining  the  size  of  wire 
to  be  used  lies  in  so  adjusting  its  resistance  plus 
that  of  the  lamps,  that  the  voltage  of  the  dynamo 
will  overcome  this  resistance.  It  is  a  problem 
that  can  be  attacked  from  many  sides. 

In  the  first  place  the  resistance  of  the  copper 
wire  of  the  conductor  may  be  taken  to  be  its 
length  in  feet  multiplied  by  10.79  and  divided 
by  its  sectional  area  in  circular  mils.  Thus  a 
mile  (5,280  ft.)  of  J^  inch  copper  wire  would 
offer  a  resistance  of 


Electric  %fgbtfns  141 


A  transposition  of  the  formula  enables  us  to 
get  the  length,  when  size  of  wire  and  resistance 
are  given,  or  the  size  of  wire  for  a  given  re- 
sistance and  length. 

The  determination  of  the  size  of  the  wire  suit- 
able for  any  circuit  depends  upon  the  resistances 
to  be  overcome  in  that  circuit.  In  calculating 
these  resistances  it  must  be  borne  in  mind  that, 
where  the  lamps  are  in  multiple  as  in  Fig.  32, 
the  total  resistance  is  lessened  with  an  increase 
in  the  number  of  lamps,  due  to  the  increased 
facilities  offered  to  the  passage  of  the  current. 

Suppose  now  we  have  25  lamps,  each  with  a 
resistance  of  150  ohms.  The  total  resistance  is, 
therefore, 

150 

—  —  •=  6  ohms. 
<*o 

Further,  if  it  is  decided  that  a  drop  of  10  per 
cent,  in  potential  can  be  allowed  in  a  wire  200 
feet  long,  we  will  have  90  per  cent,  of  the  total 
current  available  for  overcoming  lamp  resistance 
and  the  other  10  for  that  of  the  wire.  The  total 
resistance  of  lamps  and  conductors  is,  therefore, 
6  —  .9  =  6.66  ohms,  and  TV  of  this,  or  0.66  ohm, 
is  attributable  to  the  conductor  alone.  The  prob- 
lem has  now  resolved  itself  into  the  determina- 


142  jeiectricitB 

tion  of  the  size  of  wire  that,  in  a  length  of  209 
feet,  will  give  a  resistance  of  0.66  ohm. 

Taking  our  first  formula  and  transposing  we 
will  have 

200  X  10.79 
— ^ =  3,268  circular  mils. 

Extracting  the  square  root  of  this  quotient  we 
have 

1/3268  =  57, 

or  the  diameter  of  the  wire  sought  is  .057  inch, 
corresponding  to  No.  15  of  the  American  wire 
gauge. 

It  will  be  seen  from  this  that  the  resistance  to 
be  overcome  is  of  the  first  moment  in  settling 
upon  the  size  of  wire  to  be  used,  and  with  that 
in  hand  the  solution  of  the  problem  is  rapid  and 
easy. 

The  wiring  for  electric  lighting  that  has  thus 
far  been  described  relates  to  the  incandescent 
system  only.  It  differs  essentially  from  that 
used  in  arc  lighting  in  that,  in  the  latter,  the 
lamps  are  usually  connected  in  series.  So  while 
in  the  incandescent  lamp  only  enough  current 
passes  through  it  for  its  own  uses,  with  the  arc . 
lamp  the  whole  current  sent  out  to  the  circuit 
passes  through  each  and  every  lamp  in  that  circuit. 


Blectrfc  Xigbtfns  143 


The  wiring  and  connections  are  made  as  when 
a  number  of  cells  are  coupled  in  series  as  in  Fig. 
13.  That  is  to  say  a  wire  is  led  from  the  nega- 
tive terminal  of  one  lamp  to  the  positive  of  the 
next  and  so  on  through  the  series  back  to  the 
negative  terminal  of  the  dynamo. 

The  calculations  as  to  the  sizes  of  wires  to  be 
used  are  made  in  exactly  the  same  way  and  the 
same  or  even  greater  precautions  must  be  taken 
in  the  matter  of  insulation.  Wiring  for  arc  cir- 
cuits must  be  heavier  and  more  substantial  than 
in  incandescent  work  on  account  of  the  greater 
voltage  to  be  protected,  but  in  other  respects  the 
principles  of  the  insulation  remain  the  same. 

It  will  thus  be  seen  that  the  wiring  and  main- 
tenance of  an  electric  lighting  system  is  a  simple 
matter  like  other  things  electrical,  but  they  do 
require  thoughtful  care  and  attention,  else  the 
results  obtained  may  not  only  be  poor  but  dis- 
astrous. 


CHAPTER  IX  ' 

ELECTRO-PLATING 

IN  the  chapter  treating  on  the  construction 
and  operation  of  batteries  it  was  shown  that  the 
electric  current  was  generated  by  the  chemical 
decomposition  of  some  of  the  materials  that  enter 
into  the  battery.  It  has  also  been  found  that 
the  decomposition  of  the  sulphate  of  copper,  that 
is  placed  in  the  porous  jar,  is  followed  by  the  de- 
position of  an  equivalent  amount  of  copper  upon 
the  electrode.  This  electrode,  therefore,  con- 
tinually increases  in  size  and  weight  by  succes- 
sive accretions  of  this  metal.  It  is  therefore,  a 
case  of  plating  a  metal  with  itself  by  means  of 
electric  deposition. 

A  practical  application  of  this  principle  is  to 
be  found  in  the  art  of  electro-plating  in  which 
an  electric  current  is  made  to  pass  through  a 
solution  of  a  metal  with  which  it  is  desired  to 
coat  another  object.  The  solution  thus  treated 
is  decomposed  and  the  metal  thus  set  free  gathers 
upon  one  of  the  electrodes  or  terminals  of  the  cir- 
144 


145 

cult.  This  electrode  is  the  object  to  be  coated 
and  is  immersed  in  the  liquid  or  bath. 

The  work  is  done  for  both  ornamental  and 
practical  purposes  and  usually  consists  in  depos- 
iting an  expensive  metal  upon  a  cheaper  one, 
whereby  the  appearance  of  the  expensive  one  is 
obtained  with  the  weight  and  cost  of  the  cheap 
one.  The  metals  that  are  most  frequently  used  for 
electro-plating  are  copper,  nickel,  silver  and  gold. 
Other  metals  that  may  be  deposited,  with  more 
or  less  ease,  are  zinc,  tin,  lead,  cobalt,  platinum 
and  iron,  though  it  is  difficult  to  do  good  work 
with  the  latter.  These  metals  are  of  compara- 
tively little  interest  to  the  electro-plater,  and  at- 
tention will,  therefore,  be  limited  in  this  chapter 
to  the  four  metals  first  mentioned. 

The  solutions  most  commonly  used  for  electro- 
plating are,  for  copper,  the  sulphate  of  copper ; 
for  nickel,  the  double  sulphate  of  nickel  and 
ammonium ;  for  silver,  the  double  cyanide  of 
silver  and  potassium ;  and  for  gold,  the  double 
cyanide  of  gold  and  potassium.  The  prepara- 
tion of  these  solutions  will  be  considered  later. 

In  nearly  all  electrical  experiments  and  in  the 
early  stages  of  practical  electrical  development, 
as  we  know  it  to-day,  the  current  for  electro- 
plating work  was  generated  by  batteries.  But, 


146  Blectrictts 

as  the  dynamo  has  supplanted  the  battery  in 
other  classes  of  work,  so  now  it  is  exclusively 
used  where  large  quantities  are  to  be  done.  Yet, 
where  the  amount  of  plating  to  be  done  is  small, 
is  done  intermittently  or  a  current  from  a  dynamo 
is  not  available  it  is  upon  the  battery  that  the 
electro-plater  is  still  obliged  to  rely. 

The  selection  of  a  battery  for  this  class  of 
work  is  a  matter  of  somewhat  greater  impor- 
tance than  it  is  where  it  is  merely  desired  to 
secure  a  current  of  sufficient  intensity  to  ring  a 
bell  or  operate  a  telegraph  instrument.  There, 
so  long  as  the  work  is  done  it  matters  little  as 
far  as  practical  results  are  concerned,  what  may 
be  the  internal  resistance  of  the  battery  itself. 
In  electro-plating,  on  the  other  hand,  it  is  unde- 
sirable to  use  a  battery  having  a  high  internal 
resistance.  The  three  qualities  that  are  desired 
for  doing  first-class  electro-plating  work  are  high 
electromotive  force,  constancy  of  voltage  and 
low  internal  resistance,  and  these  seem  to  be 
best  embodied  in  what  is  known  as  the  Bunsen 
cell. 

Like  the  DanielFs  the  Bunsen  is  an  acid  battery 
but  using  different  materials  for  electrodes  and 
liquids.  The  four  elements  of  the  cell  are  carbon 
and  zinc  for  the  electrodes  and  sulphuric  and 


^Electroplating  147 

nitric  acid  for  the  liquids.  It  is  usually  preferred 
to  use  glazed  earthenware  for  the  outer  jar 
though  glass  can  be  used  for  the  work  where  the 
battery  is  to  be  put  in  one  place  and  not  moved. 
The  sulphuric  acid  diluted  with  from  seven  to 
fifteen  parts  of  water  is  placed  in  the  outer  jar 
and  in  it  is  immersed  the  bar  or  rod  of  zinc.  The 
inner  jar  contains  nitric  acid  of  full  commercial 
strength  and  in  this  the  carbon  electrode  is  im- 
mersed. The  latter  is  made  of  baked  coke  dust 
firmly  compressed.  The  zinc  should  be  amalga- 
mated in  order  to  insure  a  proper  working  of  the 
battery,  and  this  can  be  done  as  follows  :  First 
scrape  it  until  it  is  perfectly  clean  and  bright, 
and  free  from  all  oxidization.  The  further  de- 
tails of  the  process  are  taken  from  Niaudet. 

"  The  zincs  are  placed  on  end  in  a  bucket  of 
water  containing  one-tenth  of  sulphuric  acid, 
They  stand  out  of  the  liquid  about  half  an  inch, 
so  that  they  may  be  lifted  out  without  immersing 
one's  fingers  in  the  acid.  Three  zincs  are  placed 
at  one  time  in  the  bucket,  in  order  that  each  may 
remain  in  the  cleansing  solution  the  length  of 
time  required  for  the  amalgamation  of  the  other 
two."  For  one-half  of  the  time  that  each  zinc  re- 
mains in  the  solution  its  position  should  be 
inverted  in  order  that  the  projecting  portion 


148  Blectrfcits 

may  also  be  subjected  to  the  action  of  the 
acid. 

"  The  vessel  containing  the  mercury  for  amal- 
gamation should  be  cylindrical  and  a  little  longer 
than  the  zincs  to  be  amalgamated.  This  per- 
mits the  use  of  the  smallest  quantity  of  mercury. 
The  zincs  are  carefully  immersed  in  the  mer- 
cury and  turned  slowly  once  or  twice  to  in- 
sure the  amalgamation  of  the  entire  surface. 
When  removed  they  should  be  held  at  an  angle 
to  permit  the  superfluous  mercury  to  run  off. 
They  are  then  placed  in  an  empty  trough  ;  where, 
after  a  time,  a  quantity  of  mercury,  that  has  run 
off  will  be  found  at  the  bottom." 

The  zincs  must  be  reamalgamated  every  time 
the  battery  is  cleaned  and  the  work  should  be 
done  only  a  short  time  before  charging  so  that 
the  surface  may  be  fresh  when  first  placed  in  the 
acid.  The  zinc  will  also  be  maintained  in  a  bet- 
ter condition  while  the  battery  is  at  work  if  a 
little  mercury  is  kept  in  the  bottom  of  the  cell. 

Such  a  battery  when  carefully  adjusted  can  be 
depended  upon  to  furnish  a  constant  current  of 
about  1.8  volts  with  a  low  internal  resistance 
thus  fully  meeting  the  three  requirements  of  such 
a  battery  as  already  set  forth. 

The  Bunsen  battery  possesses  nevertheless,  one 


149 

serious  disadvantage.  While  at  work  it  emits 
fumes  of  nitrous  oxide  that  are  very  injurious  to 
,he  health  of  persons  inhaling  them.  For  this 
reason  it  should  never  be  located  in  the  room 
where  the  work  is  being  done,  but  should  be  put 
in  a  closet  that  can  be  entirely  shut  off  from  the 
workroom  and  is  itself  provided  with  an  ample 
and  separate  ventilation.  This  closet  should  be 
dry  and  cool  and  yet  not  subjected  to  a  freezing 
temperature. 

The  number  of  these  cells  to  be  used  will  be 
dependent  upon  the  work  to  be  done  and  the 
metal  to  be  deposited.  For  copper  and  nickel 
there  should  be  used  three  or  more  cells  coupled 
in  series  ;  for  silver,  two  should  be  employed  and 
for  gold  one  will  answer. 

In  the  preparation  of  the  object  to  be  electro- 
plated the  first  and  all-important  essential  is 
cleanliness.  This  cleanliness  must  be  understood 
in  a  chemical  and  not  a  mechanical  sense.  The 
surface  must  be  free  from  every  trace  of  dust, 
oil,  vegetable  or  animal  matter,  and  from  all  rust 
or  tarnish.  Thus  an  article  polished  ever  so 
brightly  and  wiped,  will  have  some  particles  of 
dust  adhering  to  it  that  will  prevent  a  suitable 
deposition  of  the  plating  metal.  Or,  if  an  article 
were  to  be  made  clean  and  were  afterwards 


150  Blectrfcfts 

touched  with  the  naked  hand  the  contact  of  the 
latter  would  soil  it  to  an  extent  that  would  re- 
sult in  the  peeling  off  of  such  plating  as  might 
afterwards  be  put  upon  it. 

In  the  same  category  as  cleanliness  must  also 
be  placed  the  surface  condition  of  the  article  to 
be  plated.  The  electro  deposition  is  exceedingly 
sensitive  and  will  faithfully  reproduce  any 
blemishes  that  may  exist  on  the  surface  of  the 
metal.  Thus,  for  example  if  there  are  any 
scratches,  pitting  or  imperfections  on  the  original, 
they  will  appear  on  the  plating  and  what  is 
more,  they  cannot  be  removed  by  subsequent 
polishing  and  burnishing.  Hence  perfection  of 
surface  condition  must  be  added  to  cleanliness. 

The  several  materials  that  are  used  as  the  base 
for  electro-plating  require  somewhat  different 
treatments  in  order  to  secure  the  necessary  clean- 
liness prior  to  the  immersion  in  the  bath. 

The  alloys  of  copper,  tin  and  nickel,  whatever 
special  name  they  may  be  passing  under  can  all 
be  treated  as  belonging  to  the  same  class.  If  the 
surface  is  in  good  mechanical  condition  so  far  as 
scratches  and  imperfections  are  concerned  the 
article  to  be  plated  may  be  immersed  or  "  dipped  " 
in  a  hot  solution  of  caustic  potash.  This  will 
remove  all  traces  of  grease  and  dirt.  If,  in  addi- 


^electroplating  151 

tion  to  this,  there  is  some  oxidization  on  the  sur- 
face, the  article  must  be  dipped  in  an  acid  bath. 
This  may  be  composed  of  one  gallon  of  water, 
two  quarts  of  sulphuric  acid  and  one  quart  of 
nitric  acid  or  proportional  quantities.  If  this 
does  not  work,  add  an  ounce  of  hydrochloric  acid 
at  intervals  until  the  desired  result  has  been  ob- 
tained. 

After  dipping,  the  articles  must  be  thoroughly 
washed  in  a  superabundance  of  fresh  water. 
There  must  be  no  scrimping  of  this  commodity, 
for,  if  the  slightest  particle  of  acid  is  left  upon 
the  metal,  oxidation  will  set  in  at  once  and  the 
surface  be  spoiled  for  plating  work. 

A  word  of  caution  must  also  be  added  regard- 
ing the  use  of  these  dips.  While  the  articles  are 
submerged  within  them  they  give  off  very  in- 
jurious and  poisonous  fumes.  The  work  should, 
therefore,  either  be  done  out  of  doors  with  the 
operator  upon  the  windward  side  of  the  vessel  or 
in  a  room  provided  with  a  special  ventilating 
hood  and  shaft  beneath  which  the  dip  is  placed 
and  through  which  a  strong  up  draft  is  created. 

Cast  iron  should  be  cleaned  in  the  same  way 
as  that  followed  for  the  ordinary  pickling  proc- 
ess by  which  the  hard  scale  and  burnt  sand  with 
which  it  is  coated  is  frequently  removed  prior  to 


152  Electricity 

machining.  This  pickle  can  be  made  by  putting 
one  part  of  sulphuric  acid  into  twenty-one  parts 
of  water  which  is  about  six  ounces  to  the  gallon. 
The  metal  must  be  allowed  to  remain  in  the 
pickle  until  the  scale  is  loosened  and  can  be 
easily  scraped  off  with  a  wire  brush.  If  it  is 
particularly  obstinate,  the  work  can  be  facilitated 
by  the  addition  of  a  little  muriatic  acid. 

When  taken  out  of  the  pickle  the  surface  must 
be  at  once  scoured  with  wet  silver  sand,  then 
rinsed  in  cold  water  and  placed  in  a  cold  potash 
solution ;  after  which  it  must  be  again  rinsed  in 
clean  water  and  instantly  placed  in  the  plating 
bath. 

Kough  wrought  iron  and  steel  may  be  treated 
in  the  same  way  though  it  is  not  necessary  that 
they  should  remain  in  the  pickling  solution  for 
so  long  a  time.  Where  a  bright  surface  is  re- 
quired, it  can  be  obtained  by  any  of  the  usual 
methods  of  polishing,  after  which  it  should  be 
dipped  in  a  hot  potash  solution  to  remove  all 
traces  of  grease. 

Rapidity  of  execution  is  one  of  the  chief  req- 
uisites in  the  preparation  of  all  iron  or  steel 
articles  for  electro-plating.  The  tendency  to 
rust  or  oxidize  when  exposed  to  the  air  is  so 
great  and  takes  place  with  such  rapidity,  and  a 


,  ^electroplating  153 

coating  that  would  be  invisible  to  the  eye  is  so 
detrimental  to  the  adherence  of  the  plating  that 
the  utmost  precautions  are  necessary  in  order  to 
secure  the  proper  surface  for  deposition. 

As  the  replating  of  old  articles- constitutes  one 
of  the  chief  sources  of  revenue  of  a  jobbing  shop, 
and  the  principal  occupation  of  the  amateur, 
their  preparation  is  a  matter  of  some  moment. 

In  the  first  place  it  is  necessary  that  they 
should  be  freed  from  all  traces  of  previous  coat- 
ing since,  from  what  has  already  been  said,  it  is 
evident  that  a  satisfactory  piece  of  work  cannot 
be  done  over  patches  and  possibly  loose  pieces  of 
old  plating. 

Gold  may  be  removed  by  dissolving  it  in  a 
solution  of  the  cyanide  of  potassium.  This  is 
done  by  immersing  it  in  the  solution  and  passing 
a  strong  current  of  electricity  through  it.  In 
making  the  battery  connections  connect  the 
article  itself  direct  to  the  positive  pole  of  the 
battery  and  immerse  a  piece  of  carbon  in  the 
liquid  and  connect  this  to  the  negative  pole. 
Silver  may  also  be  stripped  in  the  same  way. 

Nickel  may  be  removed  by  immersion  in  a 
bath  consisting  of  one  part  water,  one  part  nitric 
acid  and  four  parts  sulphuric  acid.  Great  care 
must  be  exercised  in  the  preparation  of  this 


154  BlectrfcftB 

mixture  as  it  is  accompanied  by  the  development 
of  high  temperatures.  The  work  should  be  done 
in  a  lead-lined  vessel  of  iron,  as  glass  or  earthen- 
ware would  be  almost  sure  to  be  broken  by  the 
sudden  development  of  heat. 

The  article  should  be  carefully  watched  while 
it  is  in  the  stripping  liquid  and  removed  the  in- 
stant the  coating  has  been  completely  dissolved. 
The  time  required  to  effect  this  will  depend  upon 
the  thickness  of  the  original  coating  and  may 
range  from  a  minute  or  two  to  half  an  hour. 
This  should  be  done  either  in  the  open  air  or 
under  a  ventilating  shaft. 

"With  the  old  coating  stripped  off  the  work 
should  proceed  in  the  same  way  as  with  new 
articles. 

Having  prepared  the  piece  for  plating,  it  now 
remains  to  place  it  in  a  suitable  bath  and  make 
the  proper  electrical  connections  for  the  deposi- 
tion of  the  metals.  Mr.  J.  T.  Sprague  gives  the 
following  as  the  best  alkaline  copper  solution  : 
"  Dissolve  eight  ounces  of  copper  sulphate  in  one 
quart  of  hot  distilled  water,  and  allow  it  to  cool. 
Then  add  liquid  ammonia,  stirring  in  with  a  glass 
rod  until  a  green  precipitate  has  been  formed. 
Then  add  more  ammonia  until  the  whole  mixture 
has  assumed  a  blue  tint.  Dilute  this  with  an 


Electroplating  .     155 

equal  bulk  of  cold  distilled  water  and  add  enough 
solution  of  potassium  cyanide  to  destroy  the  blue 
color  and  give  a  brown  color  to  the  solution. 
Let  it  stand  for  a  few  hours  and  then  pass  it 
through  a  calico  filter,  and  then  add  enough  dis- 
tilled water  to  make  one  gallon  of  the  solution." 

The  solution  must  then  be  placed  in  a  suitable 
vat,  which  can  best  be  made  of  enameled  iron, 
the  size  of  which  will  depend  upon  the  extent  of 
the  operations  and  the  size  of  the  articles  to  be 
plated.  It  is  well  also  to  have  some  means  of 
heating  the  liquid,  as  it  will  give  the  best  results 
when  worked  at  a  temperature  of  from  115°  to 
130°  Fahr. 

The  articles  to  be  plated  are  slung  from  a  bar 
extending  across  the  top  of  the  vat,  but  separated 
from  it.  This  bar  is  directly  connected  to  the 
negative  pole  of  the  battery.  The  wires  used 
for  slinging  the  various  objects  to  be  plated 
should  be  of  copper  of  a  size  dependent  upon  the 
weight  to  be  carried.  Ordinarily  a  ISTo.  22  wire 
will  answer  every  purpose. 

The  positive  pole  of  the  battery  is  connected 
to  a  similar  rod  from  which  a  piece  of  pure 
copper  is  suspended  in  the  solution.  This  copper 
gradually  wastes  away  as  the  deposits  gather 
upon  the  plated  article. 


156  jeiectrfcitg 

With  one  ampere  of  current,  copper  can  be  de- 
posited at  the  rate  of  about  18.16  grains  per 
hour.  The  thickness  of  the  deposit  rests  upon 
the  basis  that  about  2.25  grains  are  required  for 
a  thickness  of  one-thousandth  of  an  inch  per 
square  inch  of  surface.  Knowing  the  surface,  it 
is  then  an  easy  matter  to  estimate  the  time  re- 
quired to  make  a  deposit  of  any  desired  thickness. 

For  nickel-plating  the  double  sulphate  of 
nickel  and  ammonium  is  used.  This  may  be  pre- 
pared by  dissolving  the  crystals  of  the  double 
sulphate  in  hot  water  and  then  filtering. 

It  has  already  been  noted  that  the  current  for 
depositing  nickel  must  be  somewhat  stronger 
than  that  required  for  the  other  metals  and  it  is, 
therefore  well  to  surround  large  objects  with 
anodes  or  positive  pole  connections  so  that  the 
deposition  may  be  uniform  over  all  parts  of  the 
surface. 

Even  with  this  stronger  current  the  rate  of 
deposition  is  somewhat  slower  than  with  copper, 
being  at  the  rate  of  about  16.9  grains  per  ampere 
hour,  and  it  requires  about  2.22  grains  to  coat 
one  square  inch  of  surface  with  a  thickness  of 
one-thousandth  of  an  inch.  It  is  also  necessary 
that,  in  nickel  plating,  the  process  should  proceed 
continuously  from  the  start  to  the  finish. 


157 

The  electric  connections  are  the  same  as  in  the 
care  of  copper  and  nickel  of  course  replaces  that 
metal  as  the  anode  or  positive  pole.  The  resist- 
ance offered  to  the  passage  of  the  electric  cur- 
rent also  makes  it  desirable  to  suspend  the  anode 
close  to  the  article  to  be  plated. 

Silver  plating  is  done  by  means  of  the  double 
cyanide  of  silver  and  potassium  and  the  solution 
can  best  be  formed  by  merely  dissolving  that 
salt  in  pure  water.  This  solution  may  be  rich 
or  attenuated  according  to  the  class  of  work  to 
be  done.  It  must  simply  be  borne  in  mind  that 
the  attenuated  solution  offers  a  greater  resistance 
to  the  passage  of  the  current  than  the  richer ; 
and,  therefore,  calls  for  a  more  powerful  battery. 

Bonney  gives  the  following  instructions  for 
the  preparation  of  a  gilding  solution  of  the 
double  cyanide  of  gold  and  potassium  : 

"  Procure  five  pennyweights  of  pure  gold  leaf 
or  wire,  and  divide  it  into  two  parts ;  three 
pennyweights  of  pure  white  ninety-eight  per  cent, 
cyanide  of  potassium  and  one  quart  of  distilled 
water.  Dissolve  the  cyanide  of  potassium  in  the 
distilled  water  made  hot  in  a  good  enameled 
saucepan,  and  keep  it  at  nearly  scalding  heat 
while  making  and  working  the  gilding  solution. 
Make  up  a  battery  of  two  Bunsen  or  three 


158  Electricity 

Daniell  cells  in  series.  Hang  one  strip  of  gold 
from  the  wire  leading  to  the  negative  pole  of  the 
battery  and  the  other  from  the  wire  leading  to 
the  positive  pole.  Get  a  small  clean  white 
porous  battery  cell,  nearly  fill  it  with  the  cyanide 
of  potassium  solution,  place  it  in  the  saucepan, 
and  suspend  in  the  porous  cell  the  strip  of  gold 
connected  to  the  negative  pole  of  the  battery. 
Immerse  the  other  strip  of  gold  in  the  outer 
cyanide  solution  and  pass  the  current  of  the 
battery  from  one  to  the  other  for  two  or  three 
hours.  During  that  time  the  gold  will  have  dis- 
solved off  the  anode  or  positive  strip  and  entered 
into  combination  with  the  cyanide  of  potassium 
solution  to  form  the  double  cyanide  of  gold  and 
gilding  bath." 

The  rate  of  deposition  per  ampere  hour  for 
gold  and  silver  is  about  37.73  and  52.1  grains 
respectively. 

When  iron,  steel,  lead,  tin,  zinc,  pewter  or 
Britannia  metal  are  to  be  gold  or  silver  plated,  it 
will  be  well  to  give  them  a  preliminary  coating 
of  copper  since  this  metal  can  be  made  to  adhere 
firmly  and  gold  and  silver  cannot ;  whereas  the 
latter  can  be  readily  put  upon  the  copper. 

After  the  requisite  amount  of  plating  has  been 
done  the  first  step,  whether  the  work  be  done 


159 

with  gold,  silver,  nickel  or  copper  is  to  wash  the 
article  thoroughly  in  clean  water  and  then  dry 
in  warm  boxwood  sawdust  as  that  has  been 
found  to  be  best  adapted  for  the  purpose. 

The  proper  finishing  of  articles  requires  the 
use  of  a  polishing  lathe  with  an  outfit  of  scratch 
brushes,  formed  of  fine  stiff  brass  wire  and  of 
mops  made  of  calico  stitched  together  to  form  a 
wheel  and  with  which  rouge,  crocus  and  tripoli 
can  be  applied  for  polishing.  The  final  burnish- 
ing may  be  done  by  hand  and  consists  in  the  rub- 
bing down  of  the  compact  and  hardened  surface 
with  a  smooth  burnishing  tool. 

Thus,  it  will  be  seen,  that  while  the  work  of 
electro-plating  may  call  for  a  considerable  elab- 
oration of  detail,  the  underlying  principle  is  the 
same  as  that  by  which  the  sulphate  of  copper  is 
decomposed  and  deposited  on  the  copper  electrode 
of  an  ordinary  Daniell  cell. 


CHAPTER  X 

STORAGE  BATTERIES 

THE  storage  battery  differs  from  the  ordinary 
battery  that  has  been  heretofore  considered  in 
the  essential  peculiarities  of  its  operation.  The 
action  of  an  ordinary  battery  depends  upon  the 
presence  of  materials  arranged  in  a  certain  juxta- 
position, by  which  they  are  enabled  to  maintain 
the  generation  of  an  electric  current  for  a  definite 
period  until  they  have  been  consumed  or  con- 
verted into  other  chemical  compositions  than 
those  in  which  they  were  originally  used.  When 
this  change  has  taken  place  they  are  said  to  have 
been  consumed,  and  it  is  not  economical  to  at- 
tempt to  reconvert  them  to  their  original  condi- 
tion. It  is  a  case  analogous  to  the  steam,  boiler, 
where  fuel  is  burned  and  converted  to  carbonic 
acid  gas,  from  which  it  would  be  uneconomical 
to  attempt  to  extract  the  carbon  to  use  it  over 
again. 

The  storage  battery,  on  the  other  hand,  is 
similar  in  its  action  to  the  weight  of  a  clock. 

160 


Storage  JBattetfe0  lei 

When  the  latter  is  at  the  bottom  of  the  case  it 
can  exert  no  influence  to  propel  the  works ;  but, 
when  raised  to  the  top,  it  possesses  the  so-called 
potential  energy  of  being  able  to  keep  the  clock 
in  motion  by  its  own  descent.  This  descent  may 
require  a  longer  or  a  shorter  time,  but  through- 
out the  whole  period  of  its  duration  the  clock 
runs  at  a  uniform  speed.  The  timepiece  is  thus 
kept  in  motion  by  the  repeated  lifting  of  the 
weight  by  some  external  force. 

The  storage  battery  presents  an  analogous 
case.  As  first  put  together  the  several  elements 
have  no  such  affinity  for  each  other  as  to  lead  to 
the  formation  of  different  chemical  compositions, 
and  thus  generate  an  electrical  current.  They 
are  inert  relatively  to  each  other. 

If  now  an  electrical  current  be  made  to  pass 
through  such  a  battery,  a  change  of  chemical 
composition  of  some  of  the  elements  takes  place, 
and  when  this  has  been  done  the  new  combina- 
tions bear  the  same  relationship  to  each  other 
that  is  borne  by  the  elements  of  the  primary  bat- 
tery heretofore  considered.  They  stand  ready  to 
change  back  to  the  original  composition  and 
generate  an  electrical  current. 

When  this  reconversion  is  complete  the  battery 
is  said  to  be  exhausted  and  it  is  in  precisely  the 


162  Blectrfctts 

same  condition  as  a  clock  that  has  run  down  and 
which  must  be  wound  up  again  before  it  can  go 
on. 

As  compared  with  the  simple  primary  battery, 
the  secondary  or  storage  battery,  or  accumulator 
as  it  is  frequently  called,  possesses  the  advantage 
of  being  able  to  yield  a  very  much  greater  out- 
put of  current  for  the  same  weight  and  size.  This 
feature  alone  makes  it  available  for  many  pur- 
poses where  the  primary  battery  could  not  be 
considered,  such  as  the  propulsion  of  automobiles, 
the  lighting  of  railway  cars,  and  the  propulsion 
of  street  cars. 

The  principle  of  the  storage  battery  was  dis- 
covered early  in  the  nineteenth  century  in  con- 
nection with  the  decomposition  of  water  by 
means  of  the  electric  current.  It  is  now  a  com- 
mon and  well-known  laboratory  experiment  to 
pass  a  current  of  electricity  through  a  body  of 
water  and  thereby  effect  its  decomposition.  If 
such  a  current  is  worked  it  will  be  found  that 
oxygen  gas  will  arise  in  bubbles  from  the  wire 
leading  to  the  positive  pole  of  the  battery  and 
hydrogen  from  the  one  leading  to  the  negative. 
Suppose,  now  the  terminals  of  the  wires  used  be 
made  of  platinum  so  that  the  gas  evolved  shall 
be  free  from  oxides,  and  these  gases  be  collected 


Storage  ;©atterfe0  163 

in  bell  jars  inverted  over  the  respective  terminals 
and  the  gases  evolved  thus  separately  collected ; 
and,  after  the.  connections  to  the  battery  have 
been  broken,  the  gases  themselves  be  connected 
by  a  wire,  it  will  be  found  that  a  current  of  elec- 
tricity will  be  generated,  flowing  in  an  opposite 
direction  from  that  by  which  the  decomposition 
was  affected.  As  this  continues  the  oxygen  and 
hydrogen  will  unite  to  form  water  until  they 
have  entirely  disappeared;  when  the  flow  of 
electricity  will  cease. 

From  this  as  a  basis,  other  gas  batteries  were 
constructed,  and  finally  working  along  the  same 
lines  Gaston  Plante  in  1859  found  that  it  was 
possible  to  produce  practically  the  same  results 
with  lead  plates. 

The  original  Plante  plates  consisted  of  two 
lead  plates  with  two  sheets  of  gutta-percha  laid 
between  them  and  the  whole  rolled  together  and 
immersed  in  a  jar  of  water  acidulated  with  sul- 
phuric acid.  The  formation  of  the  plates,  as  it  is 
called,  required  a  long  time  and  consisted  in 
alternately  charging  and  discharging. 

This  method  of  forming  the  plate  was  im- 
proved upon  by  Faure  who  substituted  a  plate 
coated  with  a  paste  composed  of  the  oxide  of 
lead.  This  was  done  for  the  purpose  of  securing 


164  Electricity 

a  more  rapid  formation  of  the  cell.  In  fact  it  is 
ready  for  service  after  two  or  three  chargings. 
Considerable  difficulty  was  at  first  experienced 
by  the  peeling  off  of  the  paste  but  this  was  over- 
come by  making  the  plates  in  the  form  of  a  grid 
and  pressing  the  paste  into  the  holes  from  the 
opposite  sides  so  that  it  was  interlocked  and  thus 
held  in  position.  This  paste  is  made  of  red  lead 
and  sulphuric  acid. 

The  action  of  the  electric  current  in  the  charg- 
ing of  a  Faure  plate  is  to  convert  the  paste  on 
one  plate  to  the  peroxide  of  lead  and  to  spongy 
lead  on  the  other. 

The  liquid  employed  is  a  mixture  consisting  of 
four  volumes  of  distilled  water  and  one  of  pure 
sulphuric  acid.  In  accordance  with  the  caution 
already  given,  this  mixture  should  not  be  made 
in  the  battery  cell  on  account  of  the  heat  that  is 
developed.  It  should  be  put  together  in  a  sep- 
arate vessel  and  poured  into  the  jar  when  it  has 
become  cool.  The  tops  of  the  plates  should  be 
about  1  yz  inches  below  the  surface  of  the  liquid/ 

The  range  of  usefulness  of  the  storage  battery 
is  extending  from  day  to  day  and  small  batteries 
are  being  rapidly  introduced  for  portable  lamps 
and  household  purposes.  The  ordinary  voltage 
of  such  cells  can  be  depended  upon  to  be  about 


Storage  ^Satterfce  165 

two.  Hence  a  battery  that  is  to  be  called  upon 
to  furnish  eight  volts  would  have  to  be  provided 
with  four  cells. 

In  the  formation  of  such  a  cell  a  sheet  of  lead 
plate  may  be  used  measuring  about  8  inches  by 
6  inches  by  %  inch.  This  must  be  perforated 
with  as  large  a  number  of  holes  ^  inch  in  di- 
ameter as  can  be  drilled  or  punched  in  it  and 
still  leave  room  for  countersinking  on  each  face. 
There  should  be  at  least  seven  of  these  plates  for 
each  cell  and  they  should  be  set  into  the  acid  or 
bath  and  so  coupled  that  the  negative  and  posi- 
tive plates  alternate,  two  negative  being  on  the 
outside  as  the  odd  number  would  indicate.  A 
better  and  stronger  form  of  plate  or  grid  can  be 
obtained  by  casting  as  the  metal  can  then  be  dis- 
posed in  the  most  satisfactory  manner. 

It  will  somewhat  facilitate  the  preparation  of 
the  plates  if  the  negatives  are  filled  with  pre- 
cipitated lead  crystals  formed  by  placing  strips 
of  zinc  in  acetate  of  lead.  These  crystals  are 
quite  adhesive  and  will  remain  in  position  if  they 
are  pressed  firmly  into  the  holes  in  the  grids 
from  opposite  directions.  The  jars  for  such  cells 
should  have  an  inside  measurement  of  at  least 
11  inches  by  8  inches  by  4^  inches.  This  will 
permit  the  bottom  of  the  plates  to  be  raised  1 


166 

inch  above  the  bottom  of  the  jar,  and  to  stand 
1  inch  from  the  sides  at  their  edges  and  y2  inch 
at  their  faces.  The  jar  itself  may  be  of  glass  or 
gutta-percha. 

Care  must  be  exercised  that  the  plates  do  not 
touch  each  other  when  in  position.  They  can 
best  be  held  by  hard  wood  racks  that  have  been 
saturated  with  hot  paraffine.  These  are  simply 
blocks  about  an  inch  wide  made  to  fit  across  the 
bottom  of  the  jars  and  notched  to  receive  the 
plates,  whose  faces  should  be  about  j^  inch  apart. 
These  serve  to  steady  and  hold  the  bottom  of  the 
plates  and  the  tops  should  be  held  in  a  similar 
manner  by  a  rack  laid  across  them  and  clamped 
down  to  prevent  its  floating  away. 

In  charging,  owing  to  internal  resistances  and 
the  losses  invariably  accompanying  all  trans- 
formations of  energy,  a  somewhat  higher  voltage 
must  be  used  than  that  of  the  expected  output 
of  the  cells.  It  should,  in  fact,  be  about  25  per 
cent,  in  excess  so  that  a  current  of  about  2.5  volts 
per  cell  should  be  used.  Care  must  also  be  exer- 
cised not  to  crowd  the  charging  too  rapidly  and 
for  a  cell  like  the  one  just  described  the  rate 
should  not  be  more  than  four  amperes.  This 
may  be  increased  for  larger  cells  in  proportion  to 
the  increase  of  surface  on  the  positive  plates. 


Storage  JSattcrfes  167 

While  the  charging  can  be  done  by  means  of 
a  battery  consisting  of  Bunsen  cells  like  that 
previously  described,  it  is  a  slow  and  expensive 
process  and  should  never  be  used  where  a  current 
from  a  dynamo  circuit  is  available. 

Where  it  is  possible  to  get  access  to  one  it  will 
be  found  to  be  advantageous  to  make  connections 
with  an  incandescent  electric  lighting  circuit. 
Before  making  such  a  connection  it  will  be  neces- 
sary to  determine  which  is  the  positive  and  which 
the  negative  wire. 

The  simplest  way  of  doing  this  will  be  to  im- 
merse the  two  in  a  bowl  of  water,  keeping  them, 
at  the  same  time,  some  distance  apart.  It  has 
already  been  shown  that  the  passage  of  an  elec- 
tric current  through  water  in  this  way,  serves  to 
decompose  it  into  its  constituent  gases,  oxygen 
and  hydrogen.  As  water  is  formed  by  the  union 
of  one  atom  of  oxygen  with  two  of  hydrogen  it 
follows  that  the  bubbles  of  hydrogen  arising 
from  the  negative  wire  will  be  greatly  in  excess 
of  the  oxygen  arising  from  the  positive.  The 
wires  are,  therefore,  readily  distinguished. 

The  voltage  of  these  mains  is,  however,  usu- 
ally greatly  in  excess  of  that  allowable  for  the 
charging  of  so  small  a  number  of  cells  as  that  in- 
dicated. If  the  line  is  charged  with  a  100-volt 


168  BlectrtcftB 

current  and  it  is  desired  to  cut  it  down  to  the 
ten  volts  needed  for  the  charging  of  the  four 
cell  battery  similar  to  that  which  we  have  had 
under  consideration,  it  can  be  done  by  inserting 
incandescent  lamps  of  different  voltages  into  the 
circuit.  They  should  be  adapted  for  different 
voltages  and  be  placed  in  the  positive  wire. 
Fig.  34  shows  the  scheme  of  the  wiring  by  which 

this  may  be 
done.  This  can 
be  changed  by 

arranging     the 
FIG.  34.— METHOD  OF  CHARGING  Low   1rt  A  •  «? 

lamps    diner- 
VOLTAGE  STORAGE  BATTERY 

ently  and  using 

those  for  different  voltages  in  a  way  that  will 
readily  suggest  itself. 

In  connecting  the  battery  for  charging,  the 
positive  wire  of  the  circuit  must  be  connected  to 
the  positive  plate  of  the  battery. 

The  charging  must  be  continued  until  gas  rises 
freely  from  the  plates. 

The  time  required  to  do  this  will  depend  upon 
the  capacity  of  the  battery  and  the  current  used. 
The  four  cell  battery  above  described,  for  ex- 
ample will  have  a  capacity  of  about  twenty  am- 
pere-hours. That  is  to  say  it  will  furnish  a  cur- 
rent of  one  ampere  for  twenty  hours,  or  of  two 


Storage  ^Batteries  169 

amperes  for  ten  hours.  The  time  required  for 
charging  may  be  obtained  by  dividing  their  ca- 
pacity by  the  ampereage  of  the  current  supplied 
to  them. 

Probably  more  damage  is  done  to  the  plates  of 
a  storage  battery  by  rapid  discharging  than  by 
any  other  means.  Such  a  process  tends  to  buckle 
or  bend  the  plates  and,  when  this  occurs  to  such 
an  extent  that  the  positive  and  negative  plates 
come  into  contact,  the  battery  is  practically 
ruined.  Much  damage  of  this  kind  is  done  by 
making  direct  connections  between  the  positive 
and  negative  poles,  in  order  to  ascertain  by  the 
production  of  a  spark  whether  the  cell  is  charged 
or  not.  This  short-circuits  the  cell  and  a  few  rep- 
etitions will  be  apt  to  produce  buckling.  If 
this  information  relative  to  the  condition  of  the 
cell  is  desired,  it  can  be  best  obtained  by  the  use 
of  a  two  volt  lamp  placed  in  the  circuit  between 
the  two  poles. 

When  the  discharging  of  the  battery  is  begun 
the  voltage,  for  cells  like  those  described  will  be 
about  2J^.  It  will  soon  drop  to  2  volts  and  will 
remain  practically  constant  at  that  point  until 
the  cell  is  nearly  exhausted.  As  soon,  then,  as 
it  drops  to  1.8  volts  which  may  be  detected  by 
the  dimming  of  the  lamps  if  it  is  used  for 


170  BlectricftB 

lighting,  the  discharging  should  be  stopped  and 
recharging  be  begun  as  soon  thereafter  as  pos- 
sible. 

In  the  case  of  a  storage  battery  it  may  be  re- 
membered that  far  less  damage  is  done  by  over- 
charging than  by  allowing  it  to  stand  in  an  ex- 
hausted condition.  Where  a  battery  is  to  be  out 
of  service  for  any  length  of  time,  it  should  first 
be  fully  charged  and  then  recharged  at  intervals 
of  three  or  four  weeks  to  make  up  for  leakage 
losses. 

If  allowed  to  stand  neglected  for  any  length 
of  time,  white  patches  are  apt  to  appear  on  the 
surface  of  the  plates  and  these  can  only  be  gotten 
rid  of  by  scraping  and  then  overcharging.  Their 
reappearance  may  then  be  prevented  by  the 
addition  of  a  little  caustic  soda  to  the  electrolyte 
or  liquid. 

In  addition  to  the  evolution  of  the  gases  that 
denote  the  completion  of  the  charging  of  a  bat- 
tery, the  colors  of  the  plates  are  also  changed. 
The  positive  plate  becomes  brown  and  the  nega- 
tive a  pale  slate  color. 

As  in  other  instances  that  have  been  mentioned 
in  connection  with  electrical  work,  the  storage 
battery,  when  in  use  and  being  charged,  emits  some 
fumes  or  gases  that  are  detrimental  to  health. 


Storage  Batteries  171 

They  should,  therefore,  be  kept  in  a  well-ventilated 
apartment.  Metal  work  of  any  kind  that  is  sub- 
jected to  the  action  of  these  gases  will  be  rapidly 
corroded  and,  for  that  reason,  all  of  the  metallic 
connections,  such  as  binding  posts  and  the  like, 
that  must  necessarily  be  used  about  the  battery, 
should  be  given  a  coating  of  paraffine  for  pro- 
tection. And,  as  a  final  precaution,  let  it  be 
understood  that  no  attempt  must  ever  be  made 
to  charge  these  batteries  in  the  wrong  direction. 
Such  a  proceeding  will  be  sure  to  result  in  heat- 
ing and  a  buckling  of  the  plates.  Indeed  buck- 
ling has  been  one  of  the  most  serious  difficulties 
to  be  overcome  in  the  use  and  construction  of 
this  type  of  battery.  It  appears  however,  that 
when  a  battery  has  been  well  made  and  is  well 
cared  for  it  improves  rather  than  deteriorates  with 
age.  This  has  been  the  experience  of  those  who 
use  them  for  the  development  of  large  powers 
such  as  the  propulsion  of  street  cars  and  as 
auxiliaries  in  power  stations.  They  are,  in  fact, 
like  any  other  article  intended  for  use.  They 
must  be  well  cared  for  or  they  cannot  be  de- 
pended upon  to  render  an  efficient  service.  But 
when  given  the  proper  amount  of  attention 
they  are  among  the  most  reliable  sources  for  the 
production  of  the  electric  current. 


CHAPTER  XI 

TRANSFORMERS 

IT  has  already  appeared  that  an  electric  cur- 
rent in  one  wire  may  induce  a  current  in  an  ad- 
jacent wire.  This  induction,  however,  takes 
place  only  during  the  period  of  an  increase  or 
decrease  in  the  intensity  of  the  current. 

It  has  also  been  shown  in  earlier  chapters,  that 
the  resistance  of  a  circuit  or  wire  to  the  passage 
of  the  electric  current  is  dependent  upon  its 
length,  and  that  long  lines,  such  as  are  used  for 
telegraphic  purposes,  require  a  stronger  battery 
for  their  operation  than  do  short  ones.  This 
fact  of  the  increased  resistance  of  long  lines  is 
one  of  the  principal  causes  that  militate  against 
the  conveyance  of  electric  currents  over  great 
distances.  If  the  current  is  of  low  voltage  it 
does  not  have  sufficient  intensity  to  overcome  the 
resistance  of  the  line  unless  the  latter  is  made 
very  low  ;  and  this  low  resistance  cannot  be  ob- 
tained unless  large  masses  of  copper  are  used  as 
conductors.  The  excessive  cost  of  such  con- 

172 


{Transformers  173 

ductors  makes  their  adoption  impossible  for  com- 
mercial reasons. 

The  other  alternative  for  long  distance  trans- 
mission is  the  use  of  a  small  wire  and  a  high 
voltage.  Here  again  a  practical  difficulty  is  en- 
countered in  the  fact  that  these  excessively  high 
voltages  cannot  be  used  in  ordinary  electrical 
apparatus  and  that  they  are  exceedingly  danger- 
ous both  from  the  standpoint  of  risk  to  life  and 
as  a  cause  of  fires. 

The  means  employed  to  overcome  both  of 
these  serious  difficulties  is  to  use  a  small  wire  and 
transmit  a  current  over  it  at  an  excessively  high 
voltage,  and  then,  at  the  point  of  utilization, 
insert  a  transformer  into  the  circuit,  whereby  the 
voltage  is  greatly  decreased  and  brought  down 
to  a  point  where  it  can  be  used  in  incandescent 
lighting  circuits  and  for  motor  propulsion. 

These  circuits  are  usually  of  the  alternating 
type. 

It  will  be  remembered  that,  in  the  chapter  de- 
voted to  dynamos  and  motors,  it  was  explained 
that,  as  the  coils  of  wire  constituting  the  arma- 
ture, passed  successively  through  the  magnetic 
fields  of  the  two  field  magnets,  electric  currents 
were  set  up  in  opposite  directions  respectively ; 
and  that  it  was  the  method  of  connecting  the 


174  BlectrfcttB 

wires  to  the  commutator  that  served  to  hold  the 
outflow  of  these  currents  in  a  constant  direction, 
despite  their  change  of  direction  with  each  pas- 
sage of  the  coil  through  the  neutral  point. 

Where  these  excessively  high  voltages  (10,000 
and  upwards)  are  to  be  carried  the  wiring  of  the 
dynamo  is  so  arranged  that  the  commutator  does 
not  charge  the  polarity  of  the  current  but  the  re- 
versal does  occur  in  the  outgoing  line  just  as  it 
does  in  the  armature  coil  itself.  Such  a  current 
is  called  an  alternating  one. 

This  alternation  provides  the  very  conditions 
that  are  needed  for  the  successful  generation  of 
an  induced  current  and  it  is  produced  by  the  use 
of  the  transformer. 

Electrical  apparatus  of  this  class  has  assumed 
a  great  variety  of  forms,  by  which  attempts  have 
been  made  to  overcome  the  electrical  and  me- 
chanical difficulties  inherent  in  their  construction. 
They  are  usually  enclosed  in  water-proof  cases 
and  are  placed  out  of  doors,  so  as  to  obviate  the 
necessity  for  carrying  the  high  tension  currents 
into  a  building. 

The  making  of  a  transformer  suited  for  the 
conversion  of  these  high  tension  currents  to  low 
tension  is  a  matter  involving  great  care  both  in 
the  mechanical  work  to  be  done  and  the  elec- 


{Transformers 


175 


trical  calculations.  A  transformer  may,  how- 
ever, be  said  to  consist  merely  of  one  coil  of  wire 
placed  within  and  carefully  insulated  from  an- 
other coil.  Within  the  inner  coil  there  is  a  soft 
iron  core,  similar  to  that  of  an  electro  magnet. 
In  the  transformer,  however,  this  core  is  made 
up  of  a  number  of  plates  or  wires.  A  simple 
form  of  transformer  can  be  made,  that  is  adapted 
to  light  experi- 
mental work,  by 
using  two  coils  of 
wire  as  shown  in 
Fig.  35.  It  con- 
sists merely  of  an 
inner  coil  with  its 
wires  connected  to 
the  source  of  the 
primary  current. 
If  this  inner  coil 
be  made  up  of 
about  100  feet  of  No.  16  insulated  copper  wire 
and  the  outer  of  a  smaller  wire  of  much  greater 
length,  that  is  of -1,500  feet  of  No.  35,  the  in- 
duced current  will  be  very  perceptible  even 
though  the  primary  one  be  weak. 

For  rapidly  making  and  breaking  the  circuit 
in  the  primary  wire,  a  convenient  method  will  be 


FIG.  35.— INDUCTION  COIL 


176  Blectrfcitg 

found  to  attach  one  wire  to  a  coarse  file  and  to 
draw  the  end  of  the  other  rapidly  to  and  fro  over 
the  teeth. 

The  type  of  transformer  just  described  is  what 
is  known  as  a  Ruhmkoff  coil  and  is  intended  to 
give  a  current  of  greater  potential  or  higher 
voltage  in  the  secondary  coil  than  existed  in  the 
primary.  It  is  what  might  be  technically  called 
a  step-up  transformer,  or  one  by  which  the  volt- 
age from  the  primary  to  the  secondary  current 
is  increased. 

The  method  of  transformer  construction  that 
is  followed  at  the  present  is,  however,  that  which 
originated  with  Faraday  and  which  may  be  said 
to  consist  of  a  ring  of  iron,  serving  as  a  core, 
upon  which  successive  coils  of  wire  are  placed. 
These  coils  placed  side  by  side  form  the  primary 
and  secondary  coils  of  the  transformer.  The  ad- 
vantage possessed  by  this  ring  or  closed  circuit 
transformer  is  that  its  magnetic  resistance  is  very 
much  less  and  its  efficiency  higher. 

In  the  construction  of  a  transformer  core,  par- 
ticular attention  should  be  paid  to  the  selection 
of  the  iron  from  which  it  is  made.  As  in  the 
case  of  the  ordinary  magnet  core,  the  purest  iron 
that  is  obtainable  should  be  used.  That  is  to 
say,  it  should  be  as  free  as  possible  from  carbon, 


177 

silicon,  phosphorus,  etc.  Sometimes  a  very 
mild  steel  is  used  but  pure  iron  will  be  most 
satisfactory.  A  high  quality  of  soft  Swedish 
iron  is  probably  the  best,  and  even  this  had  bet- 
ter be  in  the  form  of  sheets,  as  in  that  form  the 
mechanical  i  m- 
purities  can  be  thor- 
oughly worked  out 
of  the  metal. 

An  example  of 
transformer  con- 
struction is  shown 
diagrammatically  in 
Fig.  36.  It  is  the 
plan  of  construction 
of  the  Dick  and 
Kennedy  transform- 
er. The  central  core  FIG.  36.—  DIAGRAM  OF  THE  DICK 
A  is  built  up  of  a  AND  KENNEDY  TRANSFORMER 
number  of  soft  iron  plates  and  is  wound  with 
the  two  coils  of  wire  C  C'  and  D  D',  one  serving 
as  the  primary  and  the  other  as  the  secondary 
coil.  The  outside  of  the  core  is  wound  with 
several  layers  of  thin  sheet  iron  B.  This  was  an 
expensive  and  cumbersome  apparatus  but  serves 
to  show  the  principle  of  construction. 

The  transformer,  then,  acting  on  the  principle 


178  Electricity 

of  induction  that  has  been  known  for  so  many 
years ;  with  no  moving  parts  and  liable  to  no 
deterioration  beyond  that  incidental  to  natural 
decay,  unless  overheated,  serves  as  the  means  by 
which  the  high  tension  currents  generated  by 
some  cheap  source  of  power,  can  be  conveyed  to 
distant  points  and  there  converted  to  voltages 
that  are  utilizable. 

With  it  is  concluded  the  description  of  the 
several  classes  of  electrical  machinery  that  have 
been  developed  and  it  serves  to  emphasize  the 
fact  of  the  simplicity  of  all  of  the  fundamental 
principles  of  the  art.  The  transformer  handling 
currents  of  thousands  of  volts,  and  the  magnet  of 
the  telephone  receiver  with  its  inappreciable  ten- 
sion are  acting  upon  one  and  the  same  principle, 
differing  only  in  degree. 


CHAPTEE  XII 

BURGLAR  ALARMS  AND   GAS   LIGHTING 

THE  burglar  alarm  is  intended  to  cause  a  bell 
to  ring  whenever  a  door  or  window  in  any  part 
of  a  house  is  opened  or  moved.  The  apparatus 
that  is  installed  for  the  purpose  is  frequently 


FIG.  37. — WIRING  FOE  BURGLAR  ALARM 

quite  elaborate  in  the  details  of  its  perfection,  t 
but  the  principle  of  action  is  as  simple  as  in 
many  other  seemingly  intricate  pieces  of  elec- 
trical apparatus. 

The  clearest  way  to  explain  the  workings  of 
the  system  is  by  reference  to  the  diagram  Fig.  37. 

179 


180  BlectrfcftB 

Here,  in  order  not  to  introduce  too  great  a 
mass  of  lines,  representative  of  the  wires  used, 
which  might  be  apt  to  lead  to  confusion,  only 
four  points  are  shown  as  protected. 

At  each  of  these  four  points  contacts  are  placed 
that  will  be  closed  whenever  a  door  or  window, 
or  whatever  other  movable  piece  may  need  pro- 
tection, is  moved.  The  simplest  form  of  contact 
consists  of  a  brass  slide  that  is  made  to  pass  over 
another  as  the  door  opens.  In  order  to  avoid 
the  necessity  of  using  a  loose  wire  to  follow  the 
movements  of  the  part,  two  strips  of  brass  may 
be  set  a  short  distance  apart  and  connected  re- 
spectively to  the  two  poles  of  the  battery.  Thus, 
for  example,  in  protecting  a  window,  lay  two 
strips  of  brass  side  by  side  from  the  top  of  the 
lower  sash  to  the  top  of  the  window  casing 
The  contact  between  them  may  be  formed  by  an 
adjustable  piece  of  brass  to  be  fastened  to  any 
desired  point  on  the  sash.  This  will  enable  the 
latter  to  be  set  to  open  any  desired  amount 
.  before  the  ringing  of  the  alarm  will  be  started. 

The  annunciator  is  the  most  complicated  part 
of  the  apparatus.  It  is  intended  to  show  at  a 
glance  the  point  at  which  the  contact  has  been 
made  and  where  the  attempt  to  enter  the  house 
is  to  be  looked  for.  In  order  to  understand  its 


JSurcUar  alarms  anO  Gas  Xtgbting          181 

construction  thoroughly  it  will  be  well  to  con- 
sider it  in  connection  with  the  wiring  of  the 
building  to  be  protected  and  the  several  points 
from  which  the  alarm  is  to  be  sounded. 

In  Fig.  37,  the  annunciator  is  shown  as  con- 
nected to  four  points  only,  namely :  two  win- 
dows and  two  doors.  The  bell  E  at  the  top  of 
the  annunciator  is  of  the  vibrating  type,  exactly 
like  that  described  in  Chapter  IV  and  illustrated 
on  page  54.  The  battery  F  may  consist  of  any 
number  of  cells,  not  less  than  three,  and  increased 
in  number  according  to  the  length  of  the  circuit 
to  be  operated.  Within  the  annunciator  there  are 
four  magnet  coils  with  an  armature,  correspond- 
ing to  the  four  points  to  be  protected.  In  addi- 
tion to  the  armature  there  is  also  a  drop  that  is 
held  up  by  a  catch  on  the  same  and  which  is 
loosened  when  the  armature  is  raised  by  the  ex- 
citation of  the  magnet. 

Let  these  four  magnets  with  their  armatures 
be  indicated  by  0,  5,  c  and  d. 

At  the  two  ends  of  the  annunciator  case  there 
are  the  binding  posts  G  and  II.  From  the  post  G 
a  wire  is  led  along  the  top  of  the  case  and  a 
branch  is  carried  off  from  it  and  connected  to 
one  end  of  each  of  the  magnet  windings  #,  J,  c 
and  d,  while  a  fifth  branch  runs  up  and  connects 


182  Electricity 

to  one  of  the  binding  posts  of  the  bell  E.  The 
binding  post  G  is  also  connected  direct  to  one  of 
the  poles  of  the  battery  by  a  wire  that  has  no 
other  connections.  A  wire  is  also  led  direct 
from  the  other  pole  of  the  battery  to  the  bind- 
ing post  H.  This  wire,  however,  has  branches 
€)c/,  g  and  h  leading  off  to  the  four  protected 
points  A,  B,  C  and  D.  Each  of  these  wires  termi- 
nates in  a  contact  at  the  four  points  mentioned 
respectively. 

One  end  of  the  coil  wires  of  the  magnets  of  <z, 
#,  c  and  d  have  been  said  to  be  connected  to  the 
binding  post  G.  The  other  ends  are  extended 
through  the  wires  *',  &,  I  and  m  to  the  second  con- 
tact points  at  the  four  respective  protected  places 
A,  B,  C  and  D. 

In  the  interior  of  the  annunciator  there  are  also 
other  connections  for  the  operation  of  the  bell. 

The  several  armatures  of  <z,  J,  c  and  d  are  made 
to  hold  the  drops  up  when  not  in  use.  These 
drops  are  each  insulated  and  connected  by  wire 
to  the  other  binding  post  of  the  bell  opposite  to 
that  to  which  the  wire  from  g  is  led.  Beneath 
each  of  the  drops  there  is  a  contact  point,  which 
is  connected  to  the  binding  post  H. 

Let  us  now  look  into  the  wiring  of  the  system. 

When  it  is  at  rest  there  is  no  complete  circuit. 


JBurglar  Blatms  anfc  (3a5  Xfgbtfng          183 

Everything  is  open.  Following  the  lines  from 
the  battery  we  go  to  the  binding  post  G,  thence 
through  the  several  coils  a,  5,  c  and  6?,  and  thence 
out  through  their  respective  wires  *',  &,  I  and  m 
to  the  four  points  A,  B,  C  and  D,  where  the  circuit 
is  broken,  while  from  the  same  point  the  wires 
fyfy  9  and  h  lead  back  to  the  opposite  pole  of  the 
battery  from  that  at  which  we  started  on  our 
outer  tracing. 

Suppose  now  the  door  at  D  is  opened.  The 
connection  between  the  wires  m  and  h  is  closed 
and  the  current  flows  from  the  positive  pole  of 
the  battery  to  G,  through  the  coil  d  and  over  the 
wires  in  and  h  back  to  the  negative  pole  of  the 
battery.  In  doing  so  it  excites  the  magnet  d, 
which  lifts  its  armature  letting  fall  the  drop. 
When  this  occurs  a  contact  is  made  uniting  the 
wire  leading  from  the  binding  post  H  to  the  drop  d 
and  that  leading  from  the  binding  post  of  the  bell 
to  the  same  point.  The  bell  circuit  is  thus  closed 
and  a  current  flows  from  the  positive  pole  of  the 
battery  to  the  binding  post  G  to  the  bell  E,  to  the 
drop  d,  to  the  binding  post  H  and  thence  back  to 
the  negative  pole  of  the  battery.  The  latter 
must,  therefore,  be  strong  enough  to  work  the 
main  circuit  to  the  protected  point  as  well  as  the 
shunt  circuit  through  the  bell. 


It  will  be  seen  that,  with  this  system  of  wiring 
and  connections,  the  ringing  of  the  bell,  when 
once  started,  continues  independently  of  the 
opening  or  closing  of  the  contact  at  the  sev- 
eral protected  points.  Hence,  if  the  intruder, 
alarmed  by  the  ringing,  hastily  closes  the  opened 
door  or  window,  it  does  not  silence  the  bell, 
which  continues  to  sound  until  the  drop  is  lifted 
to  engage  with  its  catch  on  the  armature,  and 
thus  break  the  connection  between  the  binding 
post  H  and  that  on  the  bell. 

Modifications  in  the  working  of  the  bell  can 
be  made  by  having  it  rung  by  a  spring  which  is 
released  by  the  falling  of  the  drop.  In  this  case 
there  are,  of  course,  no  electric  connections  to 
the  bell.  Another  method  is  the  use  of  a  sepa- 
rate battery  for  its  working.  In  that  case  the 
arrangement  should  be  the  same  as  that  described 
in  Chapter  IV,  and  the  connections  should  be  from 
the  battery  to  one  side  of  the  bell  and  to  the 
binding  post  II.  When  this  is  done,  there  should 
be  no  connection  between  the  negative  pole  of 
the  battery  F,  and  the  binding  post  H,  all  other 
connections  remaining  the  same. 

In  order  that  the  annunciator  may  not  operate 
at  every  opening  and  closing  of  the  door  during 
the  day  when  it  is  not  needed,  a  switch  should 


3Bur0lar  Blarms  an&  Gas  Xtgbttng          185 

be  placed  in  the  wire  between  the  binding  post  G 
and  the  positive  pole  of  the  battery,  close  to  the 
former.  This  switch  can  be  opened  in  the  morn- 
ing, thus  making  the  closing  of  the  circuit  im- 
possible, and  left  so  during  the  day,  and  closed 
the  last  thing  at  night  thus  at  once  throwing  all 
connections  into  possible  working. 

Such  a  piece  of  apparatus  as  this  should  be  fre- 
quently tested  to  see  that  it  is  in  good  working 
order.  Where  the  parts  are  allowed  to  stand 
idle  for  any  length  of  time,  the  contact  points 
are  apt  to  become  slightly  oxydized  and  may  fail 
to  effect  an  electrical  contact  at  the  crucial  mo- 
ment. Therefore,  at  least  once  a  week  the 
switch  should  be  closed  during  the  day,  and  the 
contact  made  at  each  protected  point  to  see 
whether  the  bell  will  be  properly  sounded  or  not. 

The  arrangement  of  an  annunciator  for  a  hotel 
or  office  is  nearly  the  same.  The  contacts  at  the 
several  protected  points  correspond  to  the  several 
push  buttons  in  the  rooms  of  the  guests.  The 
bell,  however,  is  not  arranged  to  ring  continu- 
ously but  only  so  long  as  the  circuit  is  closed  by 
the  pressure  on  the  button. 

The  wire  from  the  binding  post  of  the  bell  is, 
therefore,  led  direct  to  the  post  H  and  the  circuit 
through  the  coils  #,  £,  c  and  d  thus  becomes  a 


186  BlectrtcftB 

shunt  circuit  that  is  just  sufficient  to  release  the 
drop  and  expose  the  number  of  the  room  from 
which  the  call  was  sounded.  The  bell  then 
ceases  to  ring  the  instant  the  push  button  is  re- 
leased, but  the  drop  having  fallen  leaves  the 
room  number  exposed  until  it  is  again  raised  at 
the  annunciator.  In  the  construction  of  the  lat- 
ter very  light  magnetic  coils  may  be  used,  and 
the  catches  for  holding  the  drops  are  easily  ar- 
ranged so  that  by  giving  enough  leverage  a  very 
slight  pull  on  the  armature  is  quite  sufficient  to 
release  them. 

There  is  one  more  application  of  electricity  to 
domestic  and  household  purposes  that,  a  luxury 
at  first,  soon  becomes  a  necessity,  and  that  is  its 
adaptation  to  gas  lighting.  In  a  previous  chap- 
ter a  brief  outline  of  the  use  of  the  plate  machine 
for  the  production  of  an  electric  spark  for  gas 
lighting  was  given.  Such  work,  however,  is 
rarely  done  except  in  the  case  of  large  installa- 
tions where  a  great  number  of  burners  are  to  be 
lighted  or  where  they  are  placed  in  inaccessible 
locations  such  as  the  ceilings  of  theatres,  public 
halls  and  the  like. 

The  convenience  of  electricity  for  domestic 
purposes  lies  in  its  adaptability  to  use  on  single 
burners  or  on  a  small  number.  The  burners 


Burglar  Btarms  anD  Gas  Xigbtfng          187 

themselves  may  be  fitted  to  be  either  merely 
lighted  by  electricity  or  to  both  turn  on  the  gas 
and  light  it  at  the  same  time. 

In  fitting  up  any  method  of  this  sort  two 
things  must  be  borne  in  mind ;  that  the  source  of 
electrical  supply  must  be  sufficient  to  cause  spark- 
ing and  that  the  sparking  occurs  when  the  circuit 
is  broken  and  at  the  point  of 
rupture  and  not  when  it  is  closed. 

One  of    the  simplest  forms  of 
electric    gas   lighting  attachments 
is    to    be    found    in  the  ratchet 
burners    shown  in   Fig.   38.     The 
gas   is  turned  on  by  the  ordinary       FIG.  38.— 
key  and  a  pull  given  to  the  pendant.     RATCHET  GAS 
This  throws  the  wire  connected  to 
the  lever  extending  out  to  the  left  up  into  contact 
with  the  one  shown  clamped  about  the  tip  with 
a  piece  of  asbestos  insulating  material  beneath. 
The  touching  of  these  two  pieces  of  wire  closes 
the  circuit  and  as  they  separate  a  spark  is  pro- 
duced in  the  stream  of  gas,  issuing  from  the  tip, 
which  ignites   it.     The  gas  is  extinguished  by 
closing  the  cock  in  the  ordinary  manner. 

Such  a  burner  is  suited  for  use  in  kitchens, 
stables  and  other  places  where  they  are  apt  to  be 
used  by  careless  or  ignorant  persons,  as  there  is 


188  Electricity 

little  danger  of  the  gas  being  left  turned  on  un- 
lighted. 

A  more  convenient  form  of  burner  is  the  auto- 
matic whose  general  appearance  is  shown  in  Fig. 
39.     With  this  burner  the  gas  is  both  turned  on 
and  lighted  by  electricity,  and  it 
is  especially  convenient  for  use  in 
cellars  and  hallways  where  an  oc- 
casional light  is  required  and  where 

1 I    it  is  desired  to   have   the  burner 

t==J   located  at  some  distance  from  the 
L -J    entrance. 

«**•" — •  The  burner  contains  within  itself 

FIG.     39.— Au-  ..!_.,  ,.  XT  , 

TOMATIC  GAS  k°tn  the  means  of  opening  the  cock 

LIGHTEB         in   the  'gaspipe   and  the   sparking 

arrangement  for  lighting. 

When  at  rest,  the  two  terminals  that  are  shown 
leading  up  to  the  tjp  beside  the  burner  are  in  con- 
tact. Within  the  case  there  are  two  sets  of  mag- 
nets and  an  armature  that  is  moved  by  one  or 
the  other  alternately.  When  the  current  is  first 
turned  on  the  gas  valve  is  opened  and  the  arma- 
ture raised  and  turned  so  as  to  be  caught  by  a 
hook  that  holds  the  valve  open.  As  it  does  so  it 
strikes  against  a  lever  by  which  the  contact 
points  beside  the  burner  are  separated  thus  pro- 
ducing a  spark.  This  break  of  the  circuit  puts 


alarms  and  <3as  Xfsbtins          189 

an  end  to  the  attraction  of  the  magnet  and  the 
armature  drops,  allowing  the  terminals  beside  the 
burner  to  come  together  again.  Such  contact 
again  closes  the  circuit  and  energizes  the  mag- 
nets, lifting  the  armature  only  to  separate  the 
contact  points  and  produce  another  spark.  This 
vibrating  action  continues  just  as  it  does  in  the 
case  of  the  vibrating  electric  bell,  producing  a 
series  of  sparks  so  long  as  the  push  button  is  kept 
closed.  This  button  is  naturally  released  when 
the  gas  ignites. 

The  gas  is  turned  off  by  pressing  another  but- 
ton whereby  the  armature  is  brought  under  the 
influence  of  the  other  or  extinguishing  magnet. 

The  common  practice  is  to  place  the  push 
buttons  near  the  entrance  to  the  cellar  or  hall- 
way that  is  to  be  lighted  and  to  use  white  for  the 
lighting  button  and  black  for  the  extinguishing. 

In  residences,  where  the  hall  gas  is  to  be 
lighted,  the  lighting  button  may  be  placed  near 
the  front  door,  and  the  extinguished  at  the  head 
of  the  stairway ;  so  that  the  gas  may  be  lighted 
upon  entering  and  extinguishing  when  the  sec- 
ond-story has  been  reached.  It  is  also  possible 
to  have  two  or  more  lighting  and  extinguishing 
buttons  at  any  convenient  locations. 

As  for  the  battery,  the  same  rule  as  that  pre- 


190 


Electricity 


viously  laid  down  for  other  classes  of  work  holds 
good  here.  Be  sure  and  use  enough  cells  to  in- 
sure the  working.  The  number  will  depend 
upon  the  kind  of  automatic  burner  used,  but 
ordinarily  four  should  be  sufficient.  They  should 
be  connected  in  series,  and  the  arrangement  of 
the  wires  may  be  made 
in  accordance  with  the 
diagrammatic  scheme 
shown  in  Fig.  40. 

The  negative  pole  of 
the    battery    may    be 


i|l|l|!|f        ""  = 


connected  directly  to 
the  gaspipe  in  the  im- 
FIG.  40.— WIEING  FOE  AUTO-  mediate  neighborhood 
MATIC  GAS  LIGHTEE  of  jts  own  location ; 
care  being  taken  to  first  file  the  pipe  until  it  is 
bright  and  free  from  rust  and  then  wrapping  the 
copper  wire  tightly  about  it. 

The  wires  from  the  positive  pole  are  led  to  the 
two  push  buttons  and  from  them  separately  to 
the  burner  as  shown. 

It  is  quite  possible  to  operate  a  number  of 
burners  from  one  and  the  same  battery  and  the 
same  leading  wires  may  be  used.  It  is  merely  a 
matter  of  properly  locating  the  push  buttons  at 
those  points  where  it  is  desired  to  close  the  cir- 


Blarms  and  <3as  XtQbting          191 

cults.  The  same  leading  wires  can  be  used  for 
this  multiplicity  of  connections  just  as  it  was 
done  for  the  operation  of  the  burglar  alarm  from 
several  different  points  as  detailed  in  the  early 
part  of  this  chapter. 

There  is  one  more  method  of  gas  lighting  in 
common  use,  and  that  is  the  induction  coil. 

It  was  shown  in  Chapter  XI,  Fig.  35,  that  an 
induction  coil  can  be  so  constructed  as  to  raiso 
the  voltage  of  the  secondary  coil  above  that  of 
the  primary.  This  principle  is  applied  to  gas 
lighting.  A  coil  is  built  up  along  the  lines  de- 
scribed for  Fig.  34,  and  the  wires  led  off  and 
over  each  one  of  a  number  of  gas  jets  that  are 
arranged  in  one  group. 

At  each  jet  there  are  two  platinum  terminals 
sot  a  short  distance  (about  TV  inch)  apart  over 
the  burner.  The  current  from  the  induction  coil 
has  sufficient  energy  to  leap  across  this  gap  pro- 
ducing a  spark  and  igniting  the  escaping  gas. 
In  order  to  work  this  successfully,  all  of  the 
burners  in  a  group  are  left  open  and  the  gas  is 
turned  on  from  a  cock.  As  soon  as  it  is  flowing 
from  the  jets  the  spark  from  the  induction  coil 
is  used  to  ignite  it. 

The  general  arrangement  of  such  an  induction 
coil  is  shown  in  Fig.  41.  The  coil  itself  is  at  A 


192 


BlectrfcttB 


and  is  formed  by  a  comparatively  small  number 
of  turns  of  heavy  wires  for  the  primary  current 
from  the  battery ;  and  a  greater  number  of  turns 

of  fine  wire  for 
the  secondary 
current.  The 
latter  is  led  to 
the  sparkling 
tips  of  the  gas 
jets  at  B,  C  and 
D  representing 
the  group  to  be 
lighted. 

The  current 
from  the  primary  battery  E  is  carried  first 
to  a  reversing  box  F,  when  the  direction  of 
the  flow  of  the  current  through  the  wires 
G  and  H  can  be  reversed.  From  F  the  primary 
current  goes  to  the  coil  by  way  of  a  circuit 
breaker  at  I,  which  is  constructed  on  the  same 
principle  as  the  vibrating  bell  described  in 
Chapter  IY  and  illustrated  by  Fig  10.  The 
armature  K,  under  the  influence  of  the  core  of 
the  magnet,  which  should  be  formed  in  this  case, 
of  a  bundle  of  wires,  makes  and  breaks  the  cir- 
cuit exactly  as  in  the  case  of  the  bell.  This 
action  in  the  primary  circuit  causes  the  sparks 


FIG.  41. — SPARK  COIL  FOE  GAS  LIGHT- 
ING 


alarms  anfc  <5as  XfQbtins          193 

to  appear  at  the  gas  jets  in  the  secondary  cir- 
cuit. 

At  M  a  wire  comes  down  from  K  and  I  to  a 
condenser.  This  is  really  a  form  of  Ley  den  jar 
and  is  made  up  of  alternate  layers  of  tin  foil  and 
paraffine  paper.  This  condenser  serves  to  prevent 
a  spark  from  leaping  across  the  interval  between 
K  and  I  in  the  primary  current  when  the  circuit 
is  broken  and  also  to  weaken  the  secondary  cur- 
rent when  the  circuit  is  closed. 

The  intensity  of  the  current  in  the  secondary 
coil  depends  upon  the  relative  number  of  turns 
in  the  primary  and  secondary  coils  and  the 
strength  of  .the  battery  that  is  used  and  these 
may  be  varied  between  wide  limits. 


CHAPTER  XIII 

ELECTRICAL    EXPERIMENTS 

WITH  the  instruments  and  apparatus  that  have 
been  described  in  the  foregoing  chapters,  there 
are  a  large  number  of  most  interesting  experi- 
ments that  may  be  made ;  a  few  of  which  will 
be  indicated  in  the  pages  to  follow. 

First,  we  may  start  with  what  was  known  as 
the  earliest  manifestations  of  electricity  devel- 
oped by  friction.  Take  a  piece  of  sealing  wax 
or  better  a  hard  rubber  comb  and  rub  it  briskly 
for  a  moment  or  two  with  a  silk  handkerchief. 
It  will  then  be  found  to  possess  the  property  of 
lifting  small  slips  of  paper  by  attracting  them  to 
itself. 

Another  manifestation  is  produced  by  taking 
a  sheet  of  writing  paper  and  drying  it  thoroughly 
at  a  fire.  Then  lay  it  on  the  table  and  rub  it 
with  india-rubber.  It  will  adhere  to  the  surface 
upon  which  it  is  laid  and,  if  it  is  peeled  off,  will 
emit  a  crackling  sound  and  sparks  can  be  seen. 

Hang  two  pith  balls  near  each  other  by  silk 
194 


JElectrical  ^Experiments  195 

threads  and  touch  them  successively  with  a  piece 
of  excited  rubber  or  sealing  wax  and  they  will 
immediately  recede  from  each  other  and  the 
threads  will  stand  out  at  an  angle  from  the 
vertical. 

Touch  a  piece  of  pith  so-  suspended  with  an 
excited  (i.  e.,  rubbed)  glass  rod  and  it  will  imme- 
diately recede  from  the  rod  but  will  be  attracted 
to  an  excited  rod  of  sealing  wax. 

Similarly  a  number  of  pith  balls  suspended  in 
pairs  at  intervals  along  a  brass  rod,  that  is  in- 
sulated from  the  floor  and  held  in  front  of  the 
prime  conductor  of  a  plate  machine  (Fig.  2),  will 
manifest  a  like  repulsion  for  each  other.  Those 
at  the  ends  of  the  rod  will  separate  and  their 
threads  will  stand  out  at  an  angle,  while  those  at 
the  centre  will  hang  inert  and  manifest  neither 
attraction  nor  repulsion. 

The  plate  machine  can  also  be  used  to  give  an 
imitation  of  a  lightning  stroke.  Let  it  be  turned 
rapidly  and  a  conductor  connected  to  the  floor 
be  brought,  close  to  the  prime  conductor.  Sparks 
will  leap  across  the  interval  and  if  a  sheet  of 
paper  be  placed  in  the  space  it  will  be  pierced 
with  fine  holes  burned  through  it. 

By  coupling  several  Leyden  jars  together  and 
charging  them  a  longer  and  more  powerful  dis- 


196  Electricity 

charge  and  spark  can  be  obtained.  A  space  of 
six  inches  may  be  crossed.  A  thin  piece  of  wood 
held  in  the  path  of  such  a  spark  may  be  pierced 
and  shattered  in  exactly  the  same  way  as  a  tree 
is  shattered  by  a  stroke  of  lightning. 

Electrical  shocks  can  also  be  obtained  and  ad- 
ministered by  the  use  of  the  plate  machine  and 
a  Leyden  jar.  The  simplest  and  lightest  form  of 
such  a  shock  will  be  to  hold  the  knuckles  in  front 
of  the  prime  conductor  while  the  machine  is  in 
motion.  Sparks  will  leap  across  the  interval  and 
a  prickling  sensation  will  be  experienced  in  the 
hand  and  arm. 

Severer  shocks  may  be  administered  by  charg- 
ing a  Leyden  jar  and  then  discharging  it  by 
touching  the  outer  coating  and  the  knob  at  the 
same  time.  Or  the  same  shock  can  be  adminis- 
tered to  a  number  of  persons  at  once.  Let 
any  number  form  a  line  by  clasping  hands, 
and  let  the  two  at  the  ends  touch  the  outer  coat- 
ing and  knob  of  the  charged  jar  at  the  same 
time  respectively.  The  jar  will  then  be  dis- 
charged through  the  whole  line. 

It  has  been  shown  how  the  spark  from  the 
plate  machine  or  from  the  discharge  of  the  Ley- 
den jar  can  be  used  to  light  gas  at  a  distance.  A 
favorite  experiment  on  the  part  of  lecturers  on 


Electrical  Experiments  197 

electricity  is  to  use  the  spark  to  fire  a  small 
charge  of  powder  at  a  distance  from  the  speaker. 
To  do  this,  procure  a  small  cannon  and  drill  two 
touch  holes  and  line  them  with  some  insulating 
material.  Bring  to  them  the  two  wires  that  are 
to  lead  to  the  outer  coating  and  knob  of  the  jar 
respectively,  but  do  not  allow  them  to  touch. 
Load  the  cannon  and  then  by  touching  the  wires 
to  the  knob  and  outer  coating  of  the  jar,  the 
latter  will  be  discharged  and  the  spark  produced 
in  the  mass  of  powder,  will  fire  it. 

A  very  beautiful  electrical  effect  can  also  be 
produced  by  laying  wires  on  the  surface  of  an 
insulator  such  as  a  piece  of  wood.  These  wires, 
or  wire,  may  be  led  back  and  forth  over  the  sur- 
face in  parallel  lines.  Then  cut  the  wire  in  such 
a  way  that  the  points  where  this  is  done  will, 
when  taken  as  a  whole,  form  a  design,  letters  or 
words.  By  connecting  the  ends  of  the  wire  to 
the  prime  conductor  and  earth  chain  of  the  plate 
machine  and  then  rotating  the  latter,  sparks  will 
appear  at  each  point  where  the  wire  was  cut  and 
the  design  will  stand  out  in  fire  against  the  insu- 
lating background.  This  is  very  effective  when 
performed  in  the  dark. 

A  very  simple  gas  lighter  can  also  be  made 
with  a  Ley  den  jar.  Simply  charge  the  jar  and 


198  Blectrfcitg 

grasping  it  in  the  hand  turn  on  the  gas  and  touch 
the  edge  of  the  tip  with  the  knob  of  the  jar. 
The  resulting  spark  will  ignite  the  gas. 

One  of  the  most  interesting  experiments  that 
can  be  performed  with  a  battery  is  that  of  the 
decomposition  of  water.  It  has  been  shown  that 
if  an  electrical  current  be  passed  through  a  basin 
of  water  oxygen  will  be  evolved  from  the  posi- 
tive terminal  and  hydrogen  from  the  negative. 

These  two  gases  can  be  easily  collected.  Pro- 
cure two  bell  jars,  fill  them  with  water,  invert 
them  and  submerge  their  edges  in  the  water  of 
the  basin  through  which  the  current  is  to  be 
made  to  pass.  The  atmospheric  pressure  will 
keep  them  filled.  Place  the  two  terminals  be- 
neath the  jars,  one  under  each,  and  turn  on  the 
current.  The  gases  evolved  will  rise  into  the 
jars  and  displace  the  water. 

"With  the  gases  thus  obtained  a  number  of  in- 
teresting phenomena  can  be  shown.  If  they  are 
brought  together  at  a  burner  they  may  be  ig- 
nited and  burned  with  an  intensely  hot  flame. 
Or  an  extinguished  candle,  with  a  spark  on  the 
wick,  when  plunged  into  the  oxygen  jar  will 
burst  into  flame.  A  piece  of  red  hot  iron  dipped 
into  the  same  jar  will  glow  and  burn  like  tinder 
in  the  air. 


Electrical  Experiments  199 

Magnetism  also  affords  a  wide  scope  for  ex- 
perimental work.  The  formation  of  a  permanent 
magnet  is  easily  accomplished  by  simply  laying  a 
piece  of  steel  across  the  two  poles  of  a  magnet, 
like  that  used  on  electric  bells.  In  this  way  a 
very  efficient  compass  needle  may  be  produced. 

A  magnet  thus  formed  and  placed  beneath  a 
sheet  of  paper  upon  which  iron  filings  are  scat- 
tered will  cause  them  to  arrange  themselves 
along  the  lines  shown  in  Fig.  23. 

These  few  experiments  will  serve  as  sugges- 
tions for  many  others  that  can  be  performed  by 
the  utilization  of  the  various  properties  of  elec- 
trical phenomena. 

In  conclusion,  attention  is  once  more  directed 
to  the  small  number  of  really  fundamental  prin- 
ciples that  enter  into  the  manifestation  and  con- 
trol of  electrical  phenomena.  But,  few  as  these 
may  be,  it  is  readily  seen  that  they  may  be  made 
to  play  a  great  variety  of  roles  according  to  the 
circumstances  under  which  they  are  obliged  to 
act.  If,  however,  the  rules  that  have  been  laid 
down  are  thoroughly  understood  and  carefully 
followed,  there  is  practically  no  limitation  to  the 
wide  variety  of  applications  to  which  the  electric 
current  may  be  put. 


GLOSSAKY 

THE  following  are  the  definitions  of  a  few 
electrical  terms  used  in  the  foregoing  chapters. 

Ammeter. — An  instrument  for  measuring  the 
strength  of  an  electric  current.  The  readings 
are  given  in  amperes. 

Ampere. — The  "unit  of  current  strength. 
Named  after  Ampere.  One  ampere  deposits 
4.0248  grammes  of  silver  per  hour.  It  is  equal  to 
the  voltage  divided  by  the  resistance  in  ohms. 

Armature. — The  revolving  portion  of  a  dynamo 
or  motor,  containing  the  wires  in  which  the  cur- 
rent is  generated  in  the  former  or  through  which 
it  is  made  to  pass  in  order  to  give  motion  in  the 
latter. 

Battery. — An  apparatus  arranged  to  furnish  a 
continuous  flow  of  an  electric  current. 

Binding  Post. — A  means  of  fastening  the 
wires  through  which  an  electric  current  is  to  pass 
to  a  battery  or  other  apparatus.  It  usually  con- 
sists of  a  case  and  screw  by  which  the  wire  may 
be  held. 
300 


201 

Cell. — A  jar  containing  any  arrangement  of 
substances  for  the  purpose  of  obtaining  a  con- 
tinuous current  of  electricity. 

Charge. — An  accumulation  of  electricity  which, 
when  the  proper  means  are  used,  may  be  again 
discharged. 

Circuit. — The  pathway  for  an  electric  current 
from  one  pole  of  a  battery  or  dynamo  to  the 
other. 

Commutator. — That  portion  of  a  dynamo  or 
motor  that  periodically  interrupts  the  electric 
current  and  serves  to  transmit  the  current  gene- 
rated in  the  armature  to  the  main  circuit. 

Conductor. — A  substance  that  offers  but  slight 
resistance  to  the  passage  of  the  electric  current. 

Coulomb. — The  unit  of  quantity  of  current. 
Named  after  Coulomb.  It  is  the  quantity  of 
electricity  flowing  in  a  current  of  one  ampere  for 
one  second.  It  is  equal  to  101  C.  G.  S.  (centi- 
meter, gramme,  second)  units. 

C.  G.  S.— The  unit  of  electrical  measurement. 
It  represents  the  work  done  by  the  movement  of 
one  gramme,  through  a  distance  of  one  centi- 
meter in  one  second. 

Current. — The  flow  of  electricity.  The  pas- 
sage of  electricity  from  one  pole  of  a  battery,  pile, 
coil  or  dynamo  to  the  other. 


202  BlectrtcftB 

Dynamic  Electricity. — Electricity  whose  cur- 
rent has  a  continuous  flow,  though  not  neces* 
sarily  in  one  direction. 

Dynamo. — An  apparatus  for  generating  an 
electric  current  by  the  transformation  of  me- 
chanical motion. 

Electrolysis. — The  decomposition  of  chemical 
compounds  by  electricity. 

Electro-magnet. — A  bar  of  soft  iron  rendered 
temporarily  magnetic  by  the  passage  of  a  current 
of  electricity  through  a  coil  of  wire  by  which  it 
is  surrounded. 

Erg. — The  work  represented  by  one  C.  G.  S. 

Farad. — The  electric  unit  of  capacity.  Named 
after  Faraday.  It  represents  the  storage  of  one 
coulomb  in  a  condenser. 

Field  Magnet. — The  magnets  through  whose 
magnetic  fields  of  influence,  the  armature  of  a 
dynamo  or  motor  is  made  to  pass. 

Galvanic  Electricity. — An  electric  current 
generated  by  a  battery.  Synonymous  with 
dynamic  electricity.  Named  after  Galvani. 

Henry. — The  unit  of  induction.  Named  after 
Henry.  It  represents  the  induction  in  an  electric 
circuit,  when  the  induced  electro-motive  force  is 
one  volt  and  the  inducing  current  varies  at  the 
rate  of  one  ampere  per  second.  Its  value  is 


203 

109     0.    G.    S.  (centimeter,    gramme,    second) 
units. 

Induction. — The  action  which  electrified  bodies 
exert  at  a  distance  on  bodies  in  a  natural  state. 
The  generation  of  a  current  in  a  circuit  insulated 
from  that  through  which  an  electric  current  is 
passing. 

Insulator. — A  substance  which  offers  a  high 
resistance  to  the  passage  of  an  electric  cur- 
rent. 

Joule. — The  electric  unit  of  heat.  Named 
after  Joule.  It  represents  the  heat  developed  in 
a  conductor  by  one  watt  in  one  second. 

Magnetic  Field. — The  region  or  space  affected 
by  a  magnet. 

Motor. — An  apparatus  for  converting  an  elec- 
tric current  into  mechanical  motion.  The  reverse 
of  a  dynamo. 

Negative  Pole. — That  pole  or  terminal  of  a 
battery  or  dynamo  towards  which  the  electric 
current  is  supposed  to  flow. 

Ohm. — The  unit  of  electrical  resistance. 
Named  after  Ohm.  The  resistance  offered  by  a 
column  of  pure  mercury  106  centimeters  long, 
and  one  square  centimeter  in  cross-section  at  a 
temperature  of  32°  Fahr.  It  is  equal  to  109; 
G.  G.  S.  units  of  resistance. 


204  BlectricitB 

Ohmmeter. — An  instrument  for  measuring  the 
resistance  of  a  circuit. 

Pile. — A  series  of  elements  "  piled  "  upon  each 
other  forming  an  electric  generator.  First  made 
by  Yolta  and  called  a  Voltaic  pile. 

Pole. — The  terminal  points  of  a  battery,  pile 
or  dynamo  from  and  to  which  the  electric  cur- 
rent is  supposed  to  flow.  The  two  points  at  op- 
posite ends  of  a  magnetic  bar  where  the  attrac- 
tion is  the  greatest. 

Positive  Pole. — That  pole  or  terminal  of  a 
battery  or  dynamo  from  which  the  electric  cur- 
rent is  supposed  to  flow. 

Potential. — Electric  intensity.  A  term  hold- 
ing the  same  relation  to  electricity  that  level 
does  to  gravity. 

Resistance. — The  opposition  offered  by  a  con- 
ductor to  the  passage  of  an  electric  current. 

Short  Circuit. — A  circuit  through  which  a  cur- 
rent is  enabled  to  pass  and  whose  resistance  is 
less  than  that  of  the  circuit  through  which  it  is 
intended  to  pass. 

Solenoid. — A  coil  of  wire  through  which  a 
current  of  electricity  is  made  to  pass,  and  which 
is  thus  made  to  possess  many  of  the  properties  of 
a  magnet. 

Statical  Electricity. — Electricity  developed  by 


(Blossarg  205 

frictional  contact  between  bodies,  as  distinguished 
from  that  generated  by  chemical  means. 

Terminal. — The  ends  of  a  battery  or  dynamo 
to  which  the  wires  of  the  circuit  are  attached. 
Usually  applied  to  the  clamping  screw  placed  in 
that  position. 

Torque. — The  torsional  stress  put  upon  a 
motor  shaft  in  its  effort  to  turn  under  the  in- 
fluence of  the  electric  current. 

Volt. — The  unit  of  electro-motive  force. 
Named  after  Volta.  It  is  equal  to  108  C.  G.  S. 
units. 

Voltmeter. — An  instrument  used  to  measure 
the  electro-motive  force  or  voltage  of  batteries 
and  dynamos. 

Watt. — The  unit  of  electric  power,  Named 
after  Watt.  It  is  equal  to  one  volt  multiplied 
by  one  ampere  or  107  C.  G.  S.  units. 

Wattmeter. — An  instrument  for  measuring  the 
number  of  watts  or  amount  of  electric  power 
passing  over  a  circuit. 


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ETIQUETTE  There  is  no  passport  to  good  society 
bv  ASnes  ft.  Morton  Hke  good  manners.  §  Ever,  though  one 
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^  A  perusal  of  this  book  will  prevent  such  blunders.  It  is 
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LETTER   WRITING      Why  do  most  persons  dislike  to 

By  Agnes  H.  Morton  vmte  letters  ?     Is  it  not  because 

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QUOTATIONS  A  clever  compilation  of  pithy  quota- 
By  Agnes  H.  Morton  n'ons»  selected  from  a  great  variety  of 
sources,  and  alphabetically  arranged 
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quotations  in  current  use,  it  contains  many  rare  bits  of  prose 
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EPITAPHS  Even   death  has  its  humorous  side. 

By  Frederic  W.  Unger  fl  There  are  said  to  be  '*  sermons  in 
stones,"  but  when  they  are  tombstones 
there  is  many  a  smile  mixed  with  the  moral,  tj  Usually 
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By  John  H.  Bechtel  are  discovered  in  its  proverbs,  and  the 
condensed  wisdom  of  all  ages  and  afl 
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the  case  is  often  a  convincing  argument,  fl  This  volume 
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KNOWING  the  United  States  or  tell  what  yeai 

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A  DICTIONARY  OF    Mast  of  us  dislike  to  look  up  * 

MYTHOLOGY  mythological    subject    because 

By  John  H.  Bechtel  °*  *^e  time    required,  fl  This 

book   remedies    that    difficulty 

because  in  it  can  be  found  at  a  glance  just  what  is  wanted. 
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SLIPS  OF  SPEECH      Who  does  not    make    them? 

By  John  H.  Bechtel  The  best  of  us  do.  <!  Why  not 

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guide,  and  is  written  in  a  most  entertaining  and  chatty 
Style. 

HANDBOOK  OF  What  is  more   disagreeable 

PRONUNCIATION      *nan   *   faulty    pronunciation? 

By  John  H.  Bechtel  No    other    defect    so    clearly 

shows  a  lack  of  culture.  €[  This 

book  contains  over  5,000  words  on  which  most  of  us  are 
apt  to  trip.  €[  They  are  here  pronounced  in  the  clearest  and 
simplest  manner,  and  according  to  the  best  authority.  ^  It  is 
more  readily  consulted  than  a  dictionary,  and  »  ju&  <u 

•ttb. 

t 


PRACTICAL         A  new  word  ft  a  new  tool  «J  This 

SYNONYMS     book  will  not  only  enlarge  your  vocabu- 

By  John  H.  Bechtcl       Iary»  but  will  show  you  how  to  express 

the  exact  shade  of  meaning  you  have 

in  mind,  and  will  cultivate  a  more  precise  habit  of  thought 

and  speech,  fl  It  will  be  found  invaluable  to  busy  journalises, 

merchants,  lawyers,  or  clergymen,  and  as  an  aid  to  teacher* 

no  less  than  to  the  boys  and  girls  under  their  care. 

AFTER-DINNER     The  dinner  itself  may  be  ever  so 

STORIES  good,  and  yet  prove  a  failure  if  there 

By  John  Harrison  *  no  ""^  to  enliven  the  company. 

€J  Nothing  adds  so  much  zest  to  an 

occasion  of  this  kind  as  a  good  story  well  told,  flf  Here  are 

hundreds  of  the  latest,  best,  brightest,  and  most  catchy  stories, 

all  of  them  short  and  pithy,  and  so  easy  to  remember  that 

anyone  can  tefl  them  successfully.   €[  There  are  also  a 

number  of  selected  toasts  suitable  to  all  occasions. 

TOASTS  Most  men  dread  being  called  upon  to 

By  William  Pittenger  respond  to  a  toast  or  to  make  an  ad- 
dress. CJ  What  would  you  not  give  for 
the  ability  to  be  rid  of  this  embarrassment  ?  No  need  to 
give  much  when  you  can  learn  the  art  from  this  little  book. 
€J  It  will  tefl  you  how  to  do  it ;  not  only  that,  but  by  ex- 
ample it  will  show  the  way,  <J  It  is  valuable  not  alone  to 
the  novke,  but  to  the  experienced  speaker,  who  wifl  gathef 
bom  it  many  suggestion*. 

i 


THE   DEBATER'S     There  is  no  greater  ability  than 

TREASURY  the  power  of  skillful  and  forcible 

By  William  Pittcngcr  debate,   and    no    accomplishment 

more  readily  acquired  if  the  person 

is  properly  directed.  CJ  In  this  Kttle  volume  are  directions  for 
organizing  and  conducing  debating  societies  and  practical 
suggestions  for  afl  who  desire  to  discuss  questions  in  public. 
€J  There  is  also  a  list  of  over  200  questions  for  debate,  with 
arguments  both  affirmative  and  negative* 

PUNCTUATION  Few  persons  can  punctuate  properly; 
By  Paul  AHardyce  to  avo^  mistakes  many  do  not  punctu- 

ate at  all.  fl  A  perusal  of  this  book 
vvifl  remove  afl  difficulties  and  make  afl  points  clear.  If  The 
rules  are  plainly  stated  and  freely  illustrated,  thus  furnishing 
a  most  useful  volume,  fl  The  author  is  everywhere  recog- 
nized as  the  leading  authority  upon  the  subject,  and  whal 
he  has  to  say  is  practical,  concise,  and  comprehensive, 

ORATORY  Few  men  ever  enjoyed  a  wider  ex- 

By  Henry  Ward  Beecher      penence  or  achieved  a  higher  repu- 
tation in  public  speaking  than  Mr, 

Beecher.  fl  What  he  has  to  say  on  this  subject  was  bom 
of  experience,  and  his  own  inimitable  style  was  at  once  both 
statement  and  illustration  of  his  theme,  fl  This  volume  ia 
a  unique  and  masterly  treatise  on  the  fundamental  principles 
of  true  oratory* 

* 


CONVERSATION     Some  people  ate  accused  of  talk 

3y  J.  P.  Mahaffy  ing  too  much.     But  no  one  is  ever 

taken  to  task  (or  talking  too  well 

H  Of  all  the  accomplishments  of  modem  society,  that  of 
being  an  agreeable  conversationalist  holds  first  place.  Noth- 
ing is  more  delightful  or  valuable.  fl[  To  suggest  what  to 
say,  just  how  and  when  to  say  it,  is  the  general  aim  of  this 
work,  and  it  succeeds  most  admirably  in  its  purpose. 

READING  The  ability  to  read  aloud  well, 

AS  A  FINE  ART     whether  at  the  fireside  or  on  the 
By  Ernest  Legouve  Public   Platform,   is   a   fine  art 

€[  The  directions  and  sugges- 
tions contained  in  this  work  of  standard  authority  will  go  far 
toward  the  attainment  of  this  charming  accomplishment 
9  The  work  is  especially  recommended  to  teachers  and 
others  interested  in  the  instruction  of  public  school  pupils. 

CONUNDRUMS  Conundrums  sharpen  our  wits  and 
By  Dean  Rivers  ^ea<^  us  to  ^k  quickly,  fl  They  are 

also  a  source  of  infinite  amusement 
and  pleasure,  whiling  away  tedious  hours  and  putting  every- 
one in  good  humor.  fl[  This  book  contains  an  excellent  col- 
lection of  over  a  thousand  of  the  latest,  brightest,  and  most 
up-to-date  conundrums,  to  which  are  added  many  Biblical, 
poetical,  and  French  conundrums. 
I 


MAGIC  There  is  no  more  delightful  form  of  entei^ 

fty  Ellis  Stanyon  tainment  than  that  afforded  by  the  per- 
formances of  a  magician,  fl  Mysterious  as 
these  performances  appear,  they  may  be  very  readily  learned 
if  carefully  explained.  €J  This  book  embraces  full  and 
detailed  descriptions  of  all  the  well  known  tricks  with  coins, 
handkerchiefs,  hats,  flowers,  and  cards,  together  with  a 
number  of  novelties  not  previously  produced  or  explained. 
q  Fully  illustrated. 

HYPNOTISM  There  is  no  more  popular  or 

By  Edward  H.  Eldridge.  A.  M.       interesting   form    of    entertain- 
ment than  hypnotic  exhibitions, 

and  everyone  would  like  to  know  how  to  hypnotize.  ^  By 
following  the  simple  and  concise  instructions  contained  in  this 
complete  manual  anyone  may,  with  a  little  practice,  readily 
team  how  to  exercise  this  unique  and  strange  power. 

WHIST  "According   to    Cavendish"    is   now 

By  Cavendish  almost   as  familiar   an    expression    as 

Twenty-third  Edition  "according  to  Hoyle."  CJ  No  whist 
player,  whether  a  novice  or  an  expert, 
can  afford  to  be  without  the  aid  and  support  of  Cavendish. 
No  household  in  which  the  game  is  played  is  complete 
without  a  copy  of  this  book.  €J  This  edition  contains  all 
of  the  matter  found  in  the  English  publication  and  at  one- 
fourth  the  cost. 

* 


PARLOR  GAMES  "  What  shall  we  do  to  amuse  our- 
By  Helen  E.  HoIHster  selves  and  our  friends  ?  "  is  a  ques- 

tion frequently  propounded  on  rainy 

days  and  long  winter  evenings.  CJ  This  volume  most  happily 
answers  this  question,  as  it  contains  a  splendid  collection  of 
all  kinds  of  games  for  amusement,  entertainment,  and  instruc- 
tion, fj  The  games  are  adapted  to  both  old  and  young,  and 
all  classes  will  find  them  both  profitable  and  interesting. 

ASTRONOMY  :  Can  you  tell  what  causes 

The  Sun  and  His  Family      day   and  night,  seasons 

By  Julia  MacNair  Wright  anc*  years»   t^es   an^ 

eclipses?     Why  is   the 

sky  blue  and  Mars  red  ?  What  are  meteors  and  shooting 
stars  ?  C[  These  and  a  thousand  other  questions  are  answered 
in  a  most  fascinating  way  in  this  highly  interesting  volume. 
Few  books  contain  as  much  valuable  material  so  pleasantly 
packed  in  so  small  a  space.  CJ  Illustrated. 

BOTANY:  The  scientific  study  of 

The  Story  of  Plant  Life      Botany  made  as  interest- 
By  Julia  MacNair  Wright  ™S  as  a  ^Ty  tale-  <I  II  is 
better  reading  than  such 

tales,  because  of  the  profit.  €[  Each  chapter  is  devoted  to 
the  month  of  the  year  in  which  plants  of  that  month  are  in 
evidence.  Not  only  is  the  subject  treated  with  accuracy, 
but  there  is  given  much  practical  information  as  to  the  care 
and  treatment  of  plants  and  flowers.  fl[  Illustrated. 
9 


FLOWERS  t  Lvery  woman  Toves  flowers, 

HOW  to  GrOW  Them      but  few  succeed  in  growing 

By  Eben  E.  Rexford  them.      With   the    help    so 

clearly  given  in  this  book  no 

one  need  fail.  €J  It  treats  mainly  of  indoor  flowers  and  plants 
— those  for  window  gardening ;  all  about  their  selection,  care, 
soil,  air,  light,  warmth,  etc.  €J  The  chapter  on  table  decora- 
tion alone  is  worth  the  price  of  the  book.  €][  While  the  sub- 
ject of  flowers  is  quite  thoroughly  covered,  the  style  used  is 
plain,  simple,  and  free  from  all  technicalities. 

DANCING  A  complete  instructor,  beginning  with 

By  Marguerite  Wilson  ^e  nnft  positions  and  steps  and  leading 
up  to  the  square  and  round  dances, 
fl  It  contains  a  fufl  list  of  calls  for  all  of  the  square  dances, 
and  the  appropriate  music  for  each  figure,  the  etiquette  of 
the  dances,  and  1 00  figures  for  the  german.  fl  It  is  unusu- 
ally well  illustrated  by  a  large  number  of  original  drawings. 
€J  Without  doubt  the  best  book  on  the  subject. 

ASTROLOGY  If  y°u  wish  to  obtain  a  horoscope  of 
By  M.  M.  Macgregor  y°ur  entire  ^e»  or  $  y°u  would  lie  to 
know  in  what  business  or  profession  you 
will  best  succeed,  what  friends  you  should  make,  whom  you 
should  marry,  the  kind  of  a  person  to  choose  for  a  business 
partner,  or  the  time  of  the  month  in  which  to  begin  an  enter- 
prise, you  will  find  these  and  hundreds  of  other  vital  ques- 
tions solved  in  this  book  by  the  science  of  Astrology, 


GRAPHOLOGY :  Do  you  know  that  every 

How  to  Read  Character    time  you  write  five  or 
from  Handwriting  «  Hnes  vour  j™"*1  a 

By  Clifford  Howard  COmplete  ,reCA°rd  °f  *°™ 

character  ?   Anyone  who 

understands  Graphology  can  tell  by  simply  examining  your 
handwriting  just  what  sort  of  a  person  you  are.  CJ  There  is 
no  method  of  character  reading  that  is  more  interesting,  more 
trustworthy,  and  more  valuable  than  that  of  Graphology, 
and  it  is  the  aim  of  this  volume  to  enable,  anyone  to  become 
a  master  of  this  most  fascinating  art. 

PRACTICAL    PALMISTRY.     The  hand  shows  the 

By  Henry  Frith  man»  ^ut  manv  who  be- 

lieve  in  palmistry  have 

found  no  ready  access  to  its  principles.  €J  This  little  guide 
to  it  is  complete,  trustworthy,  and  yet  simple  in  arrangement. 
C|  With  this  book  and  a  little  practice  anyone  may  read 
character  surely,  recall  past  events,  and  forecast  the  future. 
«I  Fully  illustrated. 

CIVICS :  This  book  answers  a  multi- 

What  Every  Citizen      tu<^e  of  questions  of  interest  to 
Should  Know  everyone,   fl  It   gives   intelli- 

By  George  Lewis  ?e£nt'   coneise'    an<*    comPlete 

information  on  such  topics  as 

the  Monroe  Doctrine,  Behring  Sea  Controversy,  Extradition 
Treaties,  Basis  of  Taxation,  and  fully  explains  the  meaning 
of  Habeas  Corpus,  Free  Coinage,  Civil  Service,  Australian 
Ballot,  and  a  great  number  of  other  equally  interesting  subjects. 
II 


LAW,   AND   HOW  TO      ^*>st  legal  difficulties  arise 
KEEP    OUT    OF   IT      from  ignorance  of  the  minor 


By  Paschal  H.  Coggins,  Esq.  P°        of  law-   fl  T^5  book 

furnishes  to  the  busy  man  and 

woman  knowledge  of  just  such  points  as  are  most  likely  to 
arise  in  every-day  affairs,  and  thus  protects  them  against 
mental  worry  and  financial  loss.  €][  Not  only  is  this  informa- 
tion liberally  given,  but  every  point  is  so  explained  and  illus- 
trated that  the  reader  will  not  only  understand  the  law  on 
the  subject,  but  cannot  fail  to  remember  it. 

CLASSICAL  DICTIONARY  All  literature  abounds 
By  Edward  S.  Ellis,  A.  M.  in  classical  allusions,  but 

many  do  not  understand 

their  meaning.  €][  The  force  of  an  argument  or  the  beauty 
of  an  illustration  is  therefore  often  lost.  ^  To  avoid  this, 
everyone  should  have  at  hand  a  complete  dictionary  such  as 
this,  fl  It  contains  all  the  classical  allusions  worth  knowing, 
and  they  are  so  ready  of  access  as  to  require  little  or  no 
time  in  looking  up. 

PLUTARCH'S   LIVES      Plutarch  was  the  most  famou, 

By  Edward  S.  Ellis.  A.  M.  biographer  and  one  of  the  most 

delightful  essayists  who  ever 

lived.  ^[  To  him  we  are  indebted  for  an  intimate  acquaint- 
ance with  many  famous  Greeks  and  Romans  who  made 
history  and  who  still  live.  €J  This  book  is  a  condensed  form 
of  the  original  "  Lives."  CJ  All  the  personages  likely  to  be 
inquired  about  are  mentioned,  and  what  is  told  of  them  is 
just  what  one  most  wishes  to  know. 


GOLF  Golf,  to-day,  is  a  synonym  for  "out- 

By  Horace  Hutchfnson  doors"  to  thousands  of  busy  people. 
fl  This  standard  book  gives  a  com- 
plete history  of  the  game,  together  with  instructions  for  the 
selection  of  implements,  and  full  directions  for  playing. 
€J  Much  interesting  information  relating  to  celebrated  links 
and  famous  players  is  presented.  C[  A  convenient  glossary, 
together  with  the  rules  and  etiquette  of  the  game,  is 
appended. 

FIRST  AID  Lives  can  be  saved  and  much 

TO  THE   INJURED      suffering   prevented    by   the 

By  F.  J.  Warwick  study  of  this  work.  <J  What 

to  do  in  all  kinds  of  accidents, 

as  well  as  in  the  first  stages  of  illness,  with  a  brief  and  simple 
statement  of  the  human  anatomy,  constitute  the  chief  features 
of  the  book.  €[  It  is  written  in  a  plain  and  simple  way, 
easily  understood,  and  its  value  is  further  increased  by  its 
copious  illustrations. 

NURSING  Every  household  has  its  serious  illnesses, 

By  S.  Virginia  Levls  kut  ^ew  fam&es  can  afford  a  profes- 
sional nurse,  fl  This  book  is  the  next 
best  thing,  better  in  some  respects,  as  anyone  can  easily 
follow  its  instructions,  and  when  once  learned  they  are 
always  available.  €[  The  fullest  particulars  are  given  for  the 
care  of  the  sick  in  all  the  simple  as  well  as  the  serious  ail- 
ments  of  Hf e. 

* 


ELECTRICITY  An  interesting  and  thoroughly  reliable 
By  George  L  Fowler  presentation  of  the  subject  for  the  ama- 
teur or  skilled  electrician.  C[If  you  wish 
to  install  an  electric  door-bell,  construct  a  telephone,  wire  a 
house,  or  understand  the  workings  of  a  dynamo,  this  volume 
will  furnish  the  required  information.  CJ  A  practical  book  of 
inestimable  value  to  everyone. 

PHYSIOGNOMY      How  can  we  judge  whether  a  man 

By  Leila  Lomax  may  be  trusted  to  handle  money  for 

us  ?     C[  How  can  a  woman  analyze 

a  man  who  would  marry  her  ?  fl  Partly  by  words,  partly 
by  voice,  partly  by  reputation,  but  more  than  all  by  looks — 
the  shape  of  the  head,  the  set  of  the  jaw,  the  line  of  the 
mouth,  the  glance  of  the  eye.  €|  Physiognomy  as  ex- 
plained in  this  book  shows  clearly  how  to  read  character 
with  every  point  explained  by  illustrations  and  photographs. 

THE  DOG  Every  dog  owner  should  know  how  to 
By  John  Maxtee  choose  a  dog,  how  to  house  and  feed  him, 
how  to  exercise  and  train  him,  and  how  to 
get  him  back  to  condition  if  he  is  out  of  sorts.  €J  All  the 
essentials  of  dog  keeping  are  here,  from  kennel  to  show- 
bench,  and  from  biscuits  to  flea-bane.  €J  For  the  one  who 
wants  a  cheap  but  expert  dog  encyclopedia  in  little  space 
this  is  the  only  book. 

14 


HEALTH1:    HOW  TO  What  is  the  use  of    dumb 

GET  AND  KEEP  IT      bells    every    morning    and 

By  Walter  V.  Woods,  M.  D.  rigid   dieting   three   times  a 

day  when  there  is  an  open 

drain  in  the  cellar  ?  <J  Why  shield  the  baby  from  draughts 
and  then  feed  him  on  infecfted  milk  ?  ^  Do  you  know  the 
things  that  make  for  Health  ? — proper  exercise,  resl,  bath- 
ing, eating,  ventilation,  and  good  plumbing — these  are  only 
a  few  of  them.  CJ  This  book  tells  what  Health  is,  what 
makes  it,  what  hurts  it,  and  how  to  get  and  how  to  keep  it. 

CURIOUS    FACTS       Why  do  you  raise  your  hat  to  a 

By  Clifford  Howard  lady  ?    and  why  are  you  always 

careful  to  offer  the  right  hand  and 

not  the  left?  t|  Is  there  a  good  reason  for  the  buttons  on 
the  sleeve  of  your  coat  ?  ^  How  did  your  family  name 
originate  ?  tj  Is  it  true  that  it  takes  nine  tailors  to  make  a 
man,  and  if  so,  why,  forsooth  ?  fl  These  and  scores  of 
equally  interesting  questions  find  answers  here.  Open  it  at 
any  page  and  you  will  see  something  you  have  wanted  to 
know  all  your  life. 


CNJ 

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